How To date marshall amplifiers

Dating your Marshall amp head or combo from mid 1969 onwards is a pretty straight forward process as Marshall started using an alphabet system that related to the year of manufacture.  The serial numbers were stamped into the aluminium panel on the rear of the amp and between 1979 -1981 they were also on the front panel.  If the inspection sticker is still on the top of the chassis then you should be able to get the exact date it went through its final tests before being shipped out to a dealer.

The stamps are 3 separate pieces of information, the model code, the serial number and the year letter.  The models codes are generally what's listed below but you do find slight variations occasionally or sometimes one isn't included and the JCN 900's didn't have one at all.

SL/A  -  100w Super Lead

SL/B  -  100w Super Bass

S/A    -  50w Lead

ST/A  -  100w Tremelo

T/A    -  50w Tremelo

SP/    -  Super PA

A/      -  200w

RI      -  Reissue

The date codes for Marshall amplifiers between 1969 and the end of 1983 were placed at the very end of the whole serial number, then from 1984 until October 1992 the date code was placed between the model code and the digits of the serial number.  Below is a full list of the date codes, you will notice there is no 'B", as the 'A' ran for about 18 months from July 1969 through 1970, they jumped to 'C' for the start of 1971.  The letters 'I', 'O' and 'Q' were also not used but due to their similarity to numbers. 

A - July 1969 - Dec 1970

C - 1971

D - 1972

E - 1973

F - 1974

G - 1975

H - 1976

J - 1977

K - 1978

L - 1979

M - 1980

N - 1981

P - 1982

R - 1983

From 1984 until 1992 the year letter appears before the numeric digits but still continues the previous alphabetical pattern.

S - 1984

T - 1985

U - 1986

V - 1987

W - 1988

X - 1989

Y - 1990

Z - 1991 - 1992