The first thin-edge boxes
On the left Paul MacCartney's AC80/100 at Abbey Road (note the white input jacks) - to its right, a couple of amp covers, with bold cursive logo.
Serial number 117. The box serves as a model for the reproductions made by Northcoast Music. The dimensions are just a touch over 19" x 11.25" x 7" (due to the thickness of the tolex covering).
Note that there is no screw on the top edge of the back panel.
Serial number 173. Still no screw on the top edge of the back board. The dimensions of the box, however, are a fraction larger than that of no. 117 - 19" x 11.5" x 7.25". The back panel machine screws screw into aluminium blind rivet nuts.
Some thin-edge boxes have six back panel screws (ie. one now on the top edge of the panel). Above, serial numbers 177 and 178.
The first thick-edge boxes
Serial no. 221. Six back panel screws. Note the corner protectors, lacking on the thin-edge boxes.
Serial number 225 - a demonstration amp. No corner protectors. In the second image one can see the cage nut for the screw on the top edge of the back.
Serial number 392, complete with original cover, its logo off-centre. The back panel machine screws are 2BA, brass, raised countersunk, 1 1/4" long. The screw for top centre is no. 8 brass wood screw, 3/4" long. The box still has blind rivet nuts for the machine screws (rather than T-nuts, which were used later). Three of the four screws for attaching the chassis to the box (via its underside) remain: 2BA, brass, raised countersunk, 2" long.
Two fixing points on the top edge of the back panel
Boxes with a single central fixing point on the top edge of the back panel carry through to the end of the cathode bias period. Two fixings points come in with the fixed bias amps - in other words, the drop-edge of the chassis was punched or drilled differently. Two fixing points continued to be the norm until the end of production.
A very early fixed bias amp. The box may not belong to the chassis, but the back panel certainly does.
Stencilled "G-R" inside - serial numbers in the 700s
"G-R" stands for Gla-Rev., the company established by the flamboyant Henry Glass and Mr Revel.
Box that accompanied serial number 323, but not original to it. The machine screws for the back panel now screw into T-nuts behind the runners. Behind the T-nuts are strips of leather. One can be seen near the "G-R" stencil, flapping slightly loose. The internal screws securing the baffle are daubed with red paint to indicate they have been checked.
Later GlaRev boxes
to be continued......