How To Date A Marshall Amp

Marshall amplifiers made hard rock possible. While Fender and Vox amps have their place in moving electrified guitar forward, the creations of Jim Marshall fostered an entirely new sound and allowed guitarists to fill stadiums with it. Marshall amps had such precedent-setting wattage and tone that their history can hardly be separated from the history of rock itself.

We recently wrote an article detailing that rich history (which you can read here), but for those simply looking to figure out how old their Marshall amp is, we offer this shortcut. The guide below will help you quickly and clearly date Marshall amps and cabinets, without us waxing poetic about their influence.

Before we begin, a few caveats:

  • Marshall model numbers look like years. If your amp says Model 1986 on the inside, that does not mean it was made in 1986. This is probably the biggest area of confusion when dating Marshall amps.
  • True serial numbers weren't really used by Marshall until July 1969, so specimens made prior to that can only be accurately dated to a fuzzy span of several years.
  • All Marshall amps originally came with Celestion speakers, so in cases where the speakers are original, speaker date codes can be used to date earlier amps.
  • Marshall cabinets didn't officially include serial numbers until October 1992. As a result, dating cabs can be more art than science.

The best approach is to cross-reference the serial number with known features for the model during different eras and the personal account of previous owners. Getting the correct year is one thing, but getting the story behind an amp is the fun part. The guide for that is much simpler: be nice, ask questions, offer beer.

Marshall Amps By Series

If you have absolutely no idea whether your Marshall is old or new, a good place to start is the model name or series. This will give you an approximate idea of the era during which your amp was manufactured. It's also one more piece of evidence to pair with the serial number to corroborate the actual year.

The first Marshall amps were made in England starting in 1962. Production has continued there uninterrupted through today, though some lower-priced models are now made in China, India or Korea, depending on the series.

JTM-45 Models: 1962 - 1966
Bluesbreaker Combos: 1964 - 1972
Four-Digit Models (no series): 1965 - 1981
JCM 600 Series: 1997 - 1999
JCM 800 Series: 1981 - 1991
JCM 900 Series: 1990 - 1998
JCM 2000 Series: 1998 - 2008
Silver Jubilee Series: 1987 - 1989
30th Anniversary Series: 1992 - 1999
JTM Series: 1995 - 1998
35th Anniversary Series: 1997 only
Solid State 5000 Series: 1984 - 1991

Valvestate Series: 1991 - 2000
AVT Series: 2000 - 2007
Mode Four Series: 2003 - 2008
MB Series: 2006 - 2012
Hand-Wired Reissue Series: 2004 - present
JVM Series: 2007 - present
Vintage Modern Series: 2007 - present
Haze Series: 2009 - present
MA Series: 2009 - present
MG Series: 1999 - present
JDM:1 Series: 2010 - present

Some amps won't fit into these series (like the recent Class 5 Combo or various signature and limited edition models), so using the serial number will be your best bet to hone in on a specific date of manufacture.

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Marshall Serial Numbers

To find the serial number on your Marshall amp, start by looking at the back panel of your amp. For models made between 1979 - 1981, the serial number will be on the front panel.

Keep in mind that no reliable serial number information exists for pre-1969 Marshall amps, so if your amp doesn't have a number matching one of the formats below, it is likely pre-1969 and identifiable by features rather than serial number.

Click on the links here to jump directly to the serial number style that matches your instrument:

Early Models: 1962 - 1964

The earliest Marshall amp models did not have model codes or any official serialization, though some models had a simple sequential four-digit numbering system inside the back panel. These numbers supposedly started with 1001 and progressed from there, starting with 2001 at the beginning of 1964. Often these specimens produced between October 1962 and December 1964 had an offset chassis. Look for original black levant covering, a gray grille and the old block-style Marshall logo.

Model Codes Without Serial Numbers: 1965 - 1969

From January 1965 to June 1969, model codes were used but no known serial numbers accompanied them. This era saw the advent of Plexiglas panels (giving rise to the "Plexi" name) and four-digit model numbers. Amps from this era still have the block-style Marshall logo and a centered chassis.

The model codes below should help you identify which model you have, while the characteristics described for each year should help with dating.

S/ 50W
/A 200W
SL/ 100W Super Lead
SB/ 100W Super Bass
SP/ Super PA
T/ 50W Tremolo
ST/ 100W Tremolo

1965 Features

  • Cream back panels
  • JTM-45 block logos changed to gold-plated plastic script (these are rarely original, as they broke easily)
  • Small round gray cabinet feet
  • Plastic handles with larger ends compared to earlier models
  • KT66, 6L6 and 5881 tubes in the power section
  • RS Spares or Drake transformer used in the JTM-45 (the Drake rated at 8000 ohms)
  • Some JTM-100 amps appear with the JMT-45 badge in late 1965 (check for two 50W transformers and a solid state rectifier)

1966 Features

  • EL34 or 6550 tubes in the power section
  • JTM-50 and JTM-100 logos debut, indicating the amp's wattage.
  • Single 100W Drake transformer for 100W models (rated at 4000 ohms)
  • GZ34 rectifier no longer used
  • Corner-lock joints on cabinets with a quality control signature inside

1967 Features

  • Reverse JTM logo (aka "Black Flag") used for half the year, carrying over from late '66
  • Gold Plexigas back panel (as opposed to cream-colored)
  • Dagnall transformers used in the JTM-100 (replacing the Drake)
  • Chassis construction transitions from aluminum to steel in late '67

1968 Features

  • White logo (as opposed to gold)
  • Amp model prefix changed from JTM to JMP (Jim Marshall Products)
  • Transformer turned 90 degrees in comparison to earlier models (to reduce hum)
  • Curved lip under the control panel (previously straight lip)

1969 Features

  • Larger black cabinet feet circa July '69 (earlier feet were small and gray)

Model Code-Serial-Date Code: 1969 - 1983

Starting in July 1969, Marshall starting using official serial codes. They were initially broken down into three parts: the model code, the serial production number and the date code. Marshall used letters as a date code to represent year of production. It's important to note that, prior to 1984, this letter came last. The letter B was skipped, as were the letters I, O and Q since they might be confused for numbers.

Use the model codes and date codes below to determine the model and age of your amp. For example, the number S/A 8481 E tells us that this is 50W amp (S/A) made in 1973 (E), production number 8481.

Model Codes

S/ or S/A 50W
SL/ or SL/A 100W Super Lead
SB/ or SB/A 100W Super Bass
A/ or /A 200W
T/ or T/A 50 W Tremolo
ST/ or ST/A 100W Tremolo
SP/ Super PA

Date Codes 1969 - 1983

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

Model Code-Date Code-Serial: 1984 - 1992

From January 1984 to September 1992, the three-part coding was used by Marshall but the date code letter was moved from the end to the middle. The same model codes from the previous section of this article still apply, although the model code "RI" is also seen for reissues. The additional date codes for this era are below.

An example from this era might be SL/A X 10059. This would indicate a 100W Super Lead (SL/A) built in 1989 (X), production number 10059.

Date Codes 1984 - 1992

S 1984
T 1985
U 1986
V 1987
W 1988
X 1989
Y 1990
Z 1991 - 1992

Nine Digits On A Sticker: 1992 - 1997

Starting in October 1992, Marshall moved away from stamped metal plate serials and began using stickers with a xx-xxxxx-xx format serial and a bar code. Cabinets had serials at this point as well. The sticker-based nine digit scheme lasted through July 1997.

These serials are much easier to understand, as they don't include any model or date codes.

  • The first two numbers indicate the last two digits of the year of production.
  • The middle five numbers indicate the production number.
  • The last two numbers indicate the week of the year (01 - 52), out of 52 weeks.

For example, the serial number 961002334 would tell us that this amp was made in 1996 (96), production number 10023, and it was made during the 34th (34) week of that year.

Letter-Ten Digits-Letter: 1997 - Present

Starting in August 1997, Marshall moved to their current serial number scheme, which is easier to understand and gives more information than previous schemes. These current serial numbers are arranged in a letter-ten digits-letter format (A-xxxx-xx-xxxx-A). These are still found on stickers with a bar code on the back of the amp.

  • The first letter indicates where the amp was manufactured (M for England, C for China, I for India, K for Korea).
  • The next four digits indicate the year of production (1998, etc.).
  • The next two digits indicate the week of the year during which the amp was produced (01 - 52).
  • The next four digits indicate the production number.
  • The final letter indicates the voltage setting (for use in different countries - see table below).

For example, a serial number of M-2002-38-1035-B would indicate an amp made in England (M) in 2002 during the 38th week of the year, production number 1035, set up for use in the United States (B).

Voltage Codes

A 230 Volts (UK)
B 120/60 Volts (US)
C 220/50 Volts (Canada)
D 105/50/60 Volts (Japan)
E 220/60 Volts (Europe)
F 130/60 Volts (Mexico)
Z Speaker cabs (no voltage)

Celestion Speaker Codes: 1963 - Present

If the speakers in your Marshall cabinet or combo are original, they can provide another piece of evidence when determining the date of manufacture. As many cabinets did not have official serial numbers before 1992, this can be especially helpful in dating earlier specimens.

Marshall has always used Celestion speakers standard from the factory, and thankfully, Celestion has been very consistent in coding their speakers. There have been three coding schemes used by Celestion since Marshall's birth as a company, each using some combination of day, month and year.

Using the month and year codes below, and knowing what order they are in for different eras, you can easily decode a Celestion speaker's age. Example: In the mid '60s the order was day-month-year, so a code showing 13DL would indicate a speaker made on the 13th of April, 1966.

The month codes below remained consistent from 1963 forward, but there have been several eras of year codes. Check the era below that applies to your speaker.

Celestion Month Codes

A January
B February
C March
D April
E May
F June
G July
H August
J September
K October
L November
M December

Celestion Year Codes: 1963 - 1967

During this four year stretch, Celestion speaker codes followed a day-month-year format. For example, a 12KM code would indicate a speaker made on the 12th of October (K) in 1967 (M). See the year codes below through 1967. The year codes changed after this, so using other pieces of evidence to make sure you have pre-1968 speakers is important. If you have a speaker older than this, the year codes move backwards through the alphabet to A, which would be 1956.

H 1963
J 1964
K 1965
L 1966
M 1967

Celestion Year Codes: 1968 - 1991

During this era, Celestion speaker codes followed a month-year-day format. The year codes started over, with 1968 beginning at A. An example code from this era might be KQ11 - a speaker made in October (K) of 1982 (Q) on the 11th.

A 1968
B 1969
C 1970
D 1971
E 1972
F 1973
G 1974
H 1975
J 1976
K 1977
L 1978
M 1979
N 1980
P 1981
Q 1982
R 1983
S 1984
T 1985
U 1986
V 1987
W 1988
X 1989
Y 1990
Z 1991

Celestion Year Codes: 1992 - Present

Currently, Celestion speaker codes follow a day-month-year format. The year codes started over, with 1992 beginning at B, oddly enough. An example code from this era might be 21KC - a speaker made on the 21st of October (K) in 1993 (C).

B 1992
C 1993
D 1994
E 1995
F 1996
G 1997
H 1998
J 1999
K 2000
L 2001
M 2002
N 2003
P 2004
Q 2005
R 2006
S 2007
T 2008
U 2009
V 2010
W 2011
X 2012

Caveats, Exceptions, Gratitude

The serial number is one part of the puzzle when dating an amp, but cross-checking the originality of the different parts, including tubes, wiring, transformers, knobs, etc. is just as important. If you're about to put down a hefty sum on a vintage Marshall, we strongly encourage you to consult multiple sources to determine the exact age and originality of the amp.

It should also be noted that there may be some signature models and limited editions that will vary slightly from the Marshall serial number formats described here, but in general, determining the year will be the same.

We can hardly express enough how grateful we are for the hard work that the good folks at Vintage Marshall Amps website, Michael Doyle and Nick Bowcott, all of whom have done an immense amount of work to increase the accuracy and availability of information on Marshall amps.

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