Vox AC100 mark 2 potentiometer date codes
The potentiometers in Vox AC100s, as in many other Vox models, were made by "Egen Electric Limited", based on Canvey Island in Essex - for a brief overview, see this page.
Date codes were stamped as a matter of course on almost all pots. The system was straightforward: two letters - the first for the month, the second for the year.
MONTH: A-L = January to December.
YEAR: M = 1965, N = 1966, O = 1967.
"KM" = November 1965, "DN" = April 1966, and so on.
Up to, and sometimes into 1965, the resistance and taper of the pot is given first, then the date code - "500K LOG. AL" for an AC100 volume pot produced in Jan. '64, and "1 MEG LOG. AL" for a treble or bass pot produced in the same month - see this page for an example.
Thereafter, a simple part number preceded the date code - "66181" for the 500K volume pot; "66318" for the 1 Meg treble and bass pots.
By 1966, the part numbers were: "66181" for the 500K volume (as before); "67030" for the 1 Meg pot employed for treble and bass.
Early 1965 on
The new form of stamping: part numbers and date codes only, the two examples below from AC100 serial number 531, an early "100W Amplifier":
Volume pot, 500K, part no. 66181, date code "AM" = January 1965.
Tone pot, 1 Meg, part no. 66318, date code "DM" = April 1965.
Egen potentiometers with printed part numbers are first seen in AC50s from early 1966 (amps with serial numbers in the 5000s). Volume pots (500K) were no. 66181; tone pots (1 Meg) no. 66520.
Serial number 1579
Volume pot, 500K, 66181, date code "KM" = November 1965.
Bass pot, 1 Meg, 67030, date code "AN" = January 1966.
Serial number in the 1900s
A 1 Meg tone pot from an AC100 with a serial number in the 1900s - date code "EN" = May 1966.