Jennings Electronic Industries - component date codes
In common with most makers of amplifiers in the late sixties and early seventies, Jennings used RCA transistors. These always bear a date code:
The code on the transistor above is "2B" = February 1972.
The year is always given as a single digit. "9" = 1969, "0" = 1970, "1" = 1971, and so on. The month of production is indicated by the letter: A-H = January to August; J-M = September to December.
Red CCL capacitors often have the date in plain, as above: "JAN 70".
Earlier caps often have a similar date code to the one adopted by RCA, except that "I" figures in the series of months (A-L therefore for Jan. to Dec.); and the number for the year comes second.
"L9" is December 1969, and so on.
For codes of components in Vox solid state amps - the Conqueror, Defiant, Supreme, et al. - see this page on the Vox Supreme website.