VOX AC100 - UPDATES AND NEW INFO
A great pic from Mick Wall's piece on The Yardbirds - for which, click here. Photographed on Friday 6th August, 1965, morning or afternoon - at any rate, before the stage was made ready for The Yardbirds' evening performance at the National Jazz and Blues Festival, Richmond. The trolley of the AC100 at left is an early one (Mark 1) with a basket top. JMI pressed eight AC100s into service for the concert - presumably for the most part loans.
17th June (2)
"Melody Maker" magazine, 3rd August 1968. A Supreme, a T60, an AC50, an AC30 PA amp with speakers, and an AC100 with two 2 x 15" cabinets.
"Melody Maker" magazine, 31st August 1968. An AC100 amp section for £60. After some weeks it was reduced to £55.
Just to signal the start of a new website on Vox T60 amplifiers. The site will build week by week - there's a good amount of material to follow.
"Naomi and the Boys", Singapore, 1966, with three AC100s, the amp section on the left in its cover:
Note that the speakers in the cab on the left are Goodmans 241s. For surviving examples of Vox SDL cabs with these drivers see this page, and serial number 1534 here. It seems that Vox used Goodmans in 1966 in cabs destined for export, the one in the pic above (and perhaps also its SDL companion) to Singapore, the two in the links to Italy, and another to the USA.
A cardboard dealer stand from 1964 and below it a photo of one in place in a music shop door, late 1964 or early 1965 :
Sold on ebay around 2015. 16" x 12" approx. The images are archived here.
A detail from a photo of Bradley's Music Shop, Leeds, published in "Beat Instrumental" magazine, January 1965. The poster at the bottom of the door advertises the film "What a Crazy World", starring Joe Brown et al.
Vox bass amplifiers, 1963-1964, out in the sun. Vox AC80/100 serial number 178 (autumn 1964) ; Vox AC50 serial number 1034 (early 1964); Vox T60 serial number 286 (mid 1963).
Just to mention in relation to the T60 below, all three pot codes are "JJ" - October 1962. The circuit does not have the additions dated 10th October 1963 on the second schematic (OS/O62).
Photograph flipped to show the pot date code.
Below, some quick pics of an early T60 amplifier (from mid to late 1963) - serial number 268. black control panel, box without vents. The Woden transformers have the date code "LT" = November 1962. The chassis, assembled by Burndept, has the stamped serial no. 01006.
A new website on T60 amps and cabs will be online next month.
The green cover probably from 1964 and one of a pair (the other being burgundy) is not original to this amp. All cables, visible in the second pic. are, however.
Vox advert in the programme for the Daily Express "Record Star Show", Empire Pool, Wembley, 21st March 1965. The full programme is available here.
Advert in the back of Melody Maker magazine, 21st September 1968 - Jennings at this point is "Jennings Electronic Developments", based, as the ad indicates, in the old JMI Dartford Road factory. It is interesting to see that the keyword is "VOX". Exactly what sort of Vox equipment was being sold is anyone's guess - most likely older valve things stored in the sheds at the back of the premises.
Later, around 1974/1975 when Tom Jennings stepped away from "Jennings Electronic Industries" as it then was, Alan Pyne, a former Vox engineer, purchased 117-119 Dartford Road along with the sheds at back, and set up in business selling numbers of the remaining Vox amps and creating new ones from those that had been left unfinished (among other things).
There are some great recollections of Pyne on this page.
During the time of JMI's collapse - late 1967 to spring 1968 - old amps left in the sheds can hardly have been of much concern. The new line, after all, was fully solid state. And the old amps were evidently of little interest either to the new incarnation of Vox - "Vox Sound Equipment Limited" (VSEL), which had come into being in early June 1968 - see Reg Clark's account in "Beat Instrumental magazine", available on the Vox Supreme website. It may be that Tom Jennings came to some arrangement, however, about the items. The small ad in Melody Maker suggests a new undertaking, a move to sell.
For material relating to JED and JEI in 1968 and 1969, see this page.
Melody Maker, 6th January 1968. Further ads for second-hand AC100s, for the most part from 1968, to come - these may have to go on a page of their own as there are a fair few. Production had come to an end, he beat boom was over, solid state was the latest Vox thing.
A new page has been started here, gathering together dealer ads and small ads for AC100s and PA amplifiers published in English and American papers and magazines in the 1960s and 1970s. The same has been done for AC50s on the AC50 website - click here. Both pages will be updated as new material comes to hand.
Melody Maker magazine, 17 July 1965. Sets of PA Amplifiers and Line Source columns offered by PAN.
Melody Maker magazine, 21st August 1965 - part of a report on the British Musical Instrument Industries (Associated Musical Instrument Industries = A.M.I.I.) Fair at the Russell Hotel. The 150 watt P.A. Ampliifer - also signalled in the "Beat Instrumental" report (Oct. 1965) - on this page.
25th May (2)
Melody Maker magazine, 29th May 1965.
The "Vox 100 watt P.A. Ampliier" was either a MC100/4 or MC100/6 - see the catalogue detail below. The MC100/6 was first shown at the British Musical Instrument Industries fair in August 1964 and put into production soon thereafter.
JMI pricelist October 1965.
The £65 for the unit offered by PAN at the head of this entry is not bad given the price new.
More to follow soon on the PA amplifiers - details will also be posted on these pages.
Melody Maker magazine, 3rd July 1965. The "St Louis Union", winners of a heat in the National Beat Contest, pictured with an AC100 and two large box AC50s. The AC100 at this date is likely to have been a cathode biased amp (an AC80/100 in other words).
24th May (2)
An advert for the Jennings shop placed in Melody Maker magazine, 20th and 27th March 1965. The shop as it was in late 1964 is pictured below.
From "Beat Instrumental" magazine, November 1964. One can just see an AC50 or AC100 with tall bass speaker cabinet (immediately right of the tree) in the window. Click as ever for a larger image. The premises were taken over by Macaris in early 1967.
Melody Maker magazine, 16th January 1965. The drawing of the AC100 had already been circulated in late 1964 and was republished full-page in "Beat Instrumental" magazine, March and April 1965 - see this page.
Melody Maker magazine, 2nd January 1965. Quite what the "Large VOX Amp" was is anyone's guess. Presumably the "100-watt VOX Amp" was either a P.A. amplifier or an AC100.
19th May (2)
A further snippet from "Beat Instrumental" magazine relating to the 1966 Frankfurt Fair - entry below.
"Beat Instrumental", February 1966. The "new range of Vox equipment" was the 7-series, which in actual fact was not ready for sale until June/July.
"Beat Instrumental", May 1966, signalling some further delay of the new series.
The 1966 Frankfurt Music Fair.
Above, the advert placed by Vox in "Beat Instrumental" magazine, February 1966. This was taken up (below) in variant form as an advert for Vox at the Frankfurt Music Fair, 27th April - 4th May.
Above, "Melody Maker" newspaper, February 1966, advertising the company's presence at the Frankfurt Musikmesse - Hall 12, Stand 2416/7. The Vox ad for the 1967 show is here. Note that the logo of the AC100 cab has an edge outline.
Serial number 880.
Below, an aerial view of the Frankfurt Fair showing Trade Hall 12 at the back of the complex.
Frankfurt Messe, photo taken in the 1970s
The complex as it is today. Trade Hall 12 is new. Many older buildings still exist though.
"Beat Instrumental" magazine did not print a review of the 1966 show. Normally only the British Musical Industries Fair in August was given serious coverage. However, we can be fairly sure that at least some of the items pictured in the adverts were exhibited, and perhaps a new 7120:
The location of the picture above is unattested, but in terms of date, Frankfurt is certainly a possibility. Early 7120s had already been issued to the Beatles. On the other hand, the shot could perhaps have been taken at the British Musical Industries Fair mounted in Russia, July '66. The intention to exhibit 7-series amps there is noted in "Beat Instrumenal" magazine, April '66.
Guitar Center advert in the Los Angeles Times, 1st February 1970. An AC100 reduced from $1000 to $299.
For the sale of a second-hand AC100 in Ottawa in 1966, see the entry lower down this page for 14th Feb.
One of Bill's adverts in the Chicago Tribune, 18th December 1973. In other weeks, the amp is priced at $150.
7th May (2)
The date code of the blue Hunts 16uf capacitor in the preamps of a number of AC100s with serial numbers in the 1900s - starting with no. 1905 - is "UYT" = 4th week of 1966. Notes have been added where relevant on this page.
Currently on Reverb, a Triumph-made AC100 Mk 2 (one can just see the brimistor in the second pic) in box no. 1274. Typical of Triumph are the short preamp tagboard, the orange rubber grommets in the chassis pass-through holes, the plain metal shrouded transformers, and the insulated stand-offs under the fuse-holder board. No stamped chassis number. The underchassis is signed "DE" = Dave Earp, who also signed off many Vox AC50s.
The amp was long reported (incorrectly) to be in a box with serial number plate 444 - see this page. Triumph-made AC100s are often assemblages of old and new elements. The mustard capacitors in this one for instance are from 1964. However, a date somewhere in the last part of 1966 / early 1967 seems probable for the amp's manufacture.
Above, a box of Arrow Switches. Although these of not of the type used by JMI in AC80/100s and AC100s, similar boxes must have arrived at the Burndept / Vox Works in Erith. The full name of the company was "Arrow Electric Switches". Its factory premises were initially on Hangar Lane, North London (1937-1961); then Brent Road, Southall, West London (1961-1968), and finally Plymouth (1968-).
Left, the metal, ball-ended, Arrow switch used on copper-panelled AC80/100s. Right, the famous Arrow "black bat" switch used from the second third of 1965.
22nd April (2)
Below (also posted on the Vox AC50 site), a couple of 18" Celestion speakers in Jennings blue from early Foundation Bass cabs (before mid 1964). One is a T1022, the other a T1079. Both are 8ohm. The speaker on the left may have been reconed.
For a short time prior to the introduction of the Celestion 18" driver in early 1964, Vox used the Goodmans Audiom 90, marketed by Goodmans from 1962/1963.
Vox recommended using two Foundation Bass cabinets with the AC100. When the high power Audiom 91 became available in the autumn of 1964 (blue label, 100 watts, 8 ohms, against the 50 watts of the black labelled 16 ohm Audiom 91), one cabinet would just about have sufficed.
Bill Wyman was an early user of two Foundation Bass cabs with his AC80/100s and AC100s.
A note from "Beat Instrumental" magazine, September 1967. Bill mentions 100 watt units, T60 cabs, and stadiums in the States. In actual fact he meant Foundation Bass cabs rather than T60s. Evidently he got through a fair few.
An early upright bass speaker cabinet, a T60 from late 1963 - the 12" speaker on a board over the upper 15" opening. The original speakers are still inside - one T530 alnico Celestion blue, one 15" blue Tannoy. Note the perspex logo. For cabinets equipped from the outset (in 1964) with two 15" drivers, see entries further down this page.
The Jennings pages will be moved to a site of their own shortly.
5th April (2)
"The Road" playing the cinema at Hailsham, Sussex. Picture originally posted here. Hard to tell for sure but the AC100 amplifier does look as though it's in a thin-edge box.
A new page added on a well-used JEI B3 bass speaker cabinet from 1974. Late JEI speaker cabs are fairly thin on the ground these days:
The Move at the Daily Express Record Star Show, 29th March 1968, backline provided by Vox. Photo from Getty Images. It is interesting to note that Vox still thought fit to provide an AC100 alongside the new solid state amps.
An even wider version of the shot of Gerry and Pacemakers with Vox equipment. Note the logo of the bass cab. Even so, probably still a crop from the original negative.
The page of notices and ads in Beat Instrumental magazine on "Jennings Electronic Industries" is now complete for 1973. A page on 1974 will follow shortly.
18th March (2)
A promo photo of the MC5 with two AC100s, a 2x15" cabinet and a pair of column speakers.
A rare uncropped version of the promo photo of Gerry and the Pacemakers with a T60 cabinet (perspex logo) and AC30 (upside-down). For a colour pic of the band on stage in late 1964, see below, entry for 5th March.
A crossover capacitor (for the protection of a Midax horn) from a Vox AC50 or AC100 speaker cabinet. See the entry for the 24th February, below.
The black paint has worn away to reveal its specifications. The subsiduary markings seem military in character. Although no maker's name appears (or survives), the inspection stamp on the back may indicate TCC - the Telegraph Condenser Company. The final letter - "E" - could be the factory.
A new page added on the Jennings Electronic Industries (JEI) Phaser, issued in 1974. Further details will be added as they accumulate.
Recently on Leboncoin, an early Vox 2x15" bass cabinet. Logo is wood block with raised letters. One blue Tannoy (probably original), and one silver Celestion T1109 (after mid 1964), perhaps a factory replacement. The wiring looks original.
A quick note in relation to the report on the Jennings Electronic Industries stand at the Frankfurt Musikmesse, March 1974 below (6th March). It turns out that the JEI Phaser is based on a design published in "Practical Electronics" magazine, October 1974. The guys who study the detail of pedals are amazing - the thread is here. A copy of the magazine is on its way.
A JEI Phaser and original box. Further pictures to follow.
"Beat Instrumental" magazine, December 1974: Jennings (JEI) prices. The Exp. 15 combo is quite something at £267.06.
"Beat Instrumental" magazine, May 1974: a note on the Jennings Electronic Industries (JEI) showing at the Frankfurt Musikmesse in March of that year.
A rare colour shot of Gerry and the Pacemakers on stage in late 1964 venue yet to be identified, at back an early AC100 SDL. The bass set is a Foundation Bass cab and another AC100 or perhaps AC50. The large letters far left may spell "BEAT".
A detail from the pic. above. The amp has no corner protectors. One can just about see the jutting out of the basket top of an early trolley. For other bands, Beatles excepted, with early AC100s (really AC80/100s), see this page.
Some more details - all from the power section - of the all-valve Vox 100 PA amplifier added on this page..
Prices of Jennings (JEI) amplifiers compiled by "Beat Instrumental" magazine, January 1974. The costliest items were the all-valve V30 and V100, and the solid state AP50 combo. The V100 was simply an amplifier section. Its partner cab was the D4.
A new page on an all-valve Vox 100 watt public address amplifier is taking shape here.
A 2uf crossover capacitor from an AC50 or AC100 speaker cabinet. These protected the Midax horn or horns from damage by low frequency signals. Underneath the black overpainting is the standard light blue/sea-green normally found on British military (and "civilian") "box" capacitors. There appears to be no printing under the black, i.e. no maker's name or specification.
Measurements: 2 1/4" tall; 2" broad; 7/16" deep. Centres of the mounting holes are 2 3/8" apart.
Below, a similar capacitor that came in military packaging (stamped with the date 1949). It is a trifle smaller than the ones used by Vox - the centres of its mounting holes are 2 1/4" apart, for instance. But in overall form it is much closer than the TCCs and Dubiliers that commonly come up on ebay and elsewhere.
Quite whether the Vox 2uf capacitors were surplus military stock made originally by one or other company (TCC or Dubilier) for some specific (non-standard) application remains a question. It is possible of course that they were made specially for Vox.
"Beat Instrumental" magazine, December 1973 - the new-style JEI 30. Note that the amp pictured has controls at front. Surviving production units have controls on top.
Recently on ebay, a Vox 100 public address amplifier from 1966 or 1967. For more on these amps (which were produced by Triumph Electronics for Vox), see this page.
18th February (3)
The back cover of "Beat Instrumental" magazine, February 1966. One of the last UK adverts to feature the AC100.
18th February (2)
"Beat Instrumental" magazine, January 1966. The fire at the Erith Works in December 1965. For pictures of the works, see this page.
A note published in "Beat Instrumental" magazine, November 1965, on new amps issued to the Beatles by Vox. These were the AC100s seen on stage at Sheffield and elsewhere in December 1965. The amps were subsequently given to the Bee Gees. One remains in Florida. See the posting here.
Snippet published in Beat Instrumental magazine, October 1964, on the Beatles' AC100s at the British Musical Instruments (Association of Musical Instrument Industries - AMII) Trade Fair, Russell Hotel, London. The Fair ran from 24th - 29th August.
Just to add that at the time of the BMI Fair, the Beatles were on tour in the States. The "100-watt amplifiers" must have been similar ones brought along from Dartford. At the end of the Fair, JMI secured the deal with Thomas Organ to supply $1.5m of equipment.
Serial number 496 - a "100W Amplifier" (the immediate precursor of the AC100 mark 2) - currently on ebay in the States, along with a repro trolley and repro 2x15" cab. The amp has had a certain amount of new work, esp. the power section underchassis. Output transformer is a replacement; and there is something unusual about the mains unit - the second 6.3V line for the preamp seems to have gone. External condition is good.
The Ottawa Journal, 2nd June 1966. The earliest advert that has come to light so far for a second-hand AC100 in North America.
Given that full rigs were going for around $900-1000 in 1966, the advert above is probably for an amp, cab and trolley set. Below, an early advert in the UK for an amp alone (repeated from a post last year).
Rudall, Carte and Co. advert in "Crescendo" Jazz Magazine, May 1965, for a "Vox 80 Watt Bass Amp", either copper or black panel (too early for a second-hand grey), for £100.0.0 - in today's money £1750.
A bumper crop of AC100s for sale at the moment. Above, serial number 1405 currently on ebay.uk. Metal guard plate around the EL34s. Replaced choke.
A nice early "100W Amplifier" - fixed bias, the immediate predecessor of the AC100 mark 2 - appeared for sale a few days ago on ebay.it. Serial number in the low 500s. For other "100W Amplifiers", see this page.
Serial number 772 - three pics below - has come up for sale in the USA. One of the nicest early AC100 mark 2s.
The advert appeared on Craigslist earlier this week.
Currently on Reverb. The serial number scratched out at some point in the amp's past (no doubt having been liberated from its rightful owner). Red warning plaque, Amphenol connectors, single pin corners = a number somewhere in the region 800-1800.
Some notes on Woden transformers to be incorporated on this page:
AUTUMN 1962:. Batches ordered by Vox for the AC30. These had part nos 66309, 66310 and 66311 (mains, output and choke). Date codes go from H.T. (August 1962) through to A.U. (January 1963) and probably beyond. Mains and output transformers were green, the choke plain.
From a beige tolex, copper panelled AC30. One can just see the green output transformer at left.
Printing style current in 1963 and 1964 (this example from Jan. 1964).
AUTUMN 1963: A new green-topped mains transformer for the AC30 was brought in - part no. 72318 - probably the same as the 66309 but with a different winding structure. Date code J.U. (September 1963) to A.V. (January 1964) and probably beyond. These were used side-by-side with the 66310 output transformer and 66311 choke.
Above, a Woden 72318 in a copper panelled AC30 made at the Vox Burndept works at Erith.
LATE 1963:. Around 120 green-topped units ordered for the first run of AC80/100s. These are part nos 72191, 72192 and 72193 for mains, output and choke. All have date codes M.U. = December 1963.
An early copper panel AC80/100.
UNPAINTED (PLAIN METAL SHROUD) WODENS
AUTUMN 1964 For the black panel AC80/100s: 72191 mains, 72193 choke, and a new output transformer with simplified windings, part no. 79806.
For the AC30, a new set: 76852, 76853 and 76854. Earliest date codes for mains and output transformers are H.V. and J.V. (August and September 1964).
EARLY 1965: New batches of 72191, 79806 and 76854 ordered for new runs of the AC80/100 (grey panels). Mains and output units have date codes B.W. (February 1965), and the choke A.W. (January).
Grey panel, cathode biased AC100 serial number 392.
Grey panel, cathode biased AC100 serial number 392.
Note that choke part no. 76854 was dropped for a few months (it was not used in the earliest fixed bias "100W Amplifiers" - see below) but came back in thereafer. The style of printing changes again:
AC100 serial no. 724. Date code of the choke is "EW" = May 1965. Used in later "100W Amplifiers" and all early AC100 Mark 2s. Note that the resistance is cited.
100 Watt Amplifier
The 100W Amplifier (as termed on its schematic) was the immediate precursor of the AC100 Mark 2. It was fixed bias but had no brimistor. Produced late summer 1965.
AC100 serial number 520, an early "100W Amplifier".
The choke in AC100 serial number 531.
The mains and output transformers, with black shrouds, in the new fixed bias AC100s have part nos 66775 and 66776; the choke with gold-coloured frame is 66429. The five digit code is similar to Woden's. Were these a species of Woden transformer - perhaps made by a subsiduary? There are certainly not Albion, as has long been known.
At any rate the manufacturer that made these units also made the ones that later went into the Vox solid state amps, also assembled at the Erith works. One sees three letters stamped in white ink - note the "GTB" on the choke pictured above.
Mains transformer in Vox Dynamic Bass serial number 1135, late 1967 / early 1968.
The three early Westrex-made AC80/100 chassis below all have numbers scratched on the aluminium above the speaker terminal block - ie. in the same position in which chassis numbers were machine-stamped on later AC100s made at the Burndept / Westrex works in erith:
Above, serial no. 174. "119" on the chassis far left.
Above, an amp with some history, serial number plate lacking. "165" on the chassis.
Where "119" is concerned, the reference may be to "119 Dartford Road", the address of the Vox Works. What "165" refers to is anyone's guess. Ideas?
Below, a Jennings Electronic Industries AC40 (as stamped on the plate) no. 1254, with a purple JEI reverb unit and home-built JEI type box for a VSL AC30 amp. The new JEI purple range was introduced in August 1973 - see this page. An identical reverb unit is pictured here.
The items are currently in Germany.
The AC40 is already registered here
21st January (3)
Relating to this entry, below. Above, a Daly 100uf 500v capacitor from late 1962. Perhaps from a Leak audio amplifier or something of that kind (not a Vox). The date code is "TL": "T" = 1962, and "L" = November. "SCT J4" and "49/28" are likely to be the Daly codes for physical dimensions/characterics. The caps are 1 5/16" diameter, 2 15/16" tall.
Due to the fact that original 100uf filter caps have often been changed in surviving AC100s, evidence of the makes used at various points in production has to be gauged in a series of "snapshots".
For copper panelled amps (serial nos 101-225) the picture is clear: gold-coloured Dubiliers were employed. And gold 100uf Dubiliers were probably also fitted in the grey panel AC80/100s made at the Burndept/Vox Works in Erith from the spring of 1965 (serial nos c. 320-430). But in many of these amps the caps have been replaced.
100uf Daly caps, on the other hand, seem to have been bought in by Westrex (along with new sets of Woden transformers and new batches of TCC capacitors) for the black panelled amps (serial numbers c. 230-330) in late 1964. Shortly thereafter production of the AC100 (AC80/100) passed to Erith. Later on, in the autumn of 1965, Daly was used again however - for the "100W Amplifier" (serial nos 431-724).
Above, the 100uf Daly filter cap in AC100 serial no. 520. The date code is "WD" = April 1965.
21st January (2)
Recently surfaced (end of last year) serial number 2103. The amp conforms to schematic OS/167, first instance dated July 1967 and redrawn in the "Vox Sound Equipment Limited" era (mid 1968 to early 1970), though no AC100 has yet come to light with a VSEL serial number plate. One can see one of the pairs of main filter capacitors, a feature of the new circuit, through the top grille. For further late amps of this type, see this page.
Number 2103 is currently in Germany, where it has been for some time. A good number of these late AC100s were exported to Europe; a few also to the U.S.A.
The chassis made at the Burndept / Vox Works in Erith for the grey panel AC80/100s - serial numbers 320-430 - have distinctive cut-outs for the main filter caps: notably two semi-circular excrescences to the main roundel.
These excrescences are not found in the earlier chassis made at Westrex, nor in the chassis later made at the Erith works for the "100W Amplifier" (serial numbers c. 431-724).
20th January (2)
Above, two preamp valve cathode bypass capacitors - Hunts 25uf - from AC80/100 serial number 392. They had both bubbled out. Date of manufacture is given in "I YT". For an overview of the Hunts date code system, see this page on the AC50 website.
Effectively "I YT" translates as "3 04" which should mean the 4th week of 1963. But Hunts was often quirky in stamping its codes, and it is possible that "3 04" was actually intended to mean the 30th week of '64.
Above a Daly capacitor from a late Westrex-made cathode biased AC80/100 - before and after some cleaning of the paint this morning. The amp is pictured here and below. One can now see the date code: "VK" = October 1964 - much in line with the dates of other components: TCC capacitors in the preamp "VJ" and "VK"; cathode bias resistors and capacitors (also TCC) which still survive, "VK".
Left, one of the pics from ebay July 2007. Centre, the amp as it now is, with a replaced mains transformer (from an AC100 Mark 2, new shroud). Right, a pic of the preamp by the input jacks. The box is probably from a later amp (serial no. 1297 on the plate).
The amp has for some time had a grey panel. However, it may not be original. As the third pic shows, two holes for extra inputs (?) were made in the aluminium chassis at some point. These do not figure on the current panel.
It seems possible, given the dates of the components in the amp, that if there was indeed a predecessor panel it was black. Note that the shroud of the mains transformer in serial no. 262 has the code "KV" = October 1964.
On the other hand, it could simply be that the existing panel was taken off for the making of the holes and then, after a change of mind (ie. a decision not to make holes in it), put back on untouched - in which case the amp must have have been one of the first cathode-biased AC80/100s to have been done in grey - a serial number potentially therefore in the 290s or low 300s.
But to go to all the bother of taking the panel off, making the holes, and then sticking the panel back on seems a little perverse. The first scenario - that the current panel is in fact a replacement for a hacked original - seems most plausible.
The spraying of the steel chassis black - done at a guess in the 70s - was presumably an attempt to retard heat. Up until 2007 the amp had its original Welwyn 270R cathode resistors (which still survive, as mentioned, along with all other original components now removed). Clearly at some point their value shifted: they currently measure around 250R. The valves and transformers will have run very hot indeed.
The sprayer did a relatively good job, but missed the backs of the transformers and managed to get the bat of the mains switch.
The gearing up of Westrex for new runs of AC80/100s in late 1964 doubtless came as a consequence of orders coming in from the USA - JMI's deal with Thomas Organ was struck in August. See the info being assembled on this page.
Serial numbers 236 and 262 have probably long been in the States - 262's cab (an SDL) unfortunately perished. Midax horns said to be from it still exist. However, numbers 249 and 276 were bought from new in the UK; number 269 was exported to Finland.
Just to add, that the majority of amps with serial numbers in the range 230 - 300 will have been made between November 1964 and February 1965. Remember that component date codes are simply a terminus post quem - a "date after which" - for the making of an amp. We do not know precisely how long capacitors / resistors / transformers sat on stockroom shelves - probably not long, but there will always have been exceptions.