Dating a Marshall amplifier can be a daunting task for even the most savvy of suitors — Amp Archives is here to help.
1962 – 1964
The earliest Marshall amplifiers were made in 1962 and had no model or serial numbers. From 1962 until 1964 Marshall amplifiers were identified by a four-digit sequential number inside the back panel, reportedly starting with 1001 in 1962 and reaching 2001 at the beginning of 1964.
1965 – 1969
Beginning in 1965 Marshall abandoned the four-digit numbering system and began using model numbers, sometimes called series numbers and model codes. While there are serial-like numbers during this era, no standard serial number format has been identified.
The model numbers can be somewhat confusing because model numbers such as 1987 or 1959 can be mistakenly interpreted as the production year of the amplifier. Amplifiers from this era must be dated within this time span based on their features, or component manufacturers and codes, including speakers, potentiometers and transformers.
- Back panels are cream colored.
- JTM-45 block logos changed to gold-plated plastic script, these are fragile and many have been replaced.
- Cabinet feet are small round and gray.
- Handles changed to plastic with larger end cap.
- Power tubes are KT66, 6L6 and 5881.
- RS Spares or Drake transformer, rated at 8000 ohms, used in the JTM-45.
- Some JTM-100 amps from late 1965 have the JMT-45 badge.
- Power tubes are EL34 or 6550.
- JTM-45 logo changed to JTM-50 and JTM-100 indicating the amp’s wattage.
- Single 100W Drake transformer, rated at 4000 ohms, part number 784-084, for 100W models.
- Single 50W Drake output transformers rated at 3,400 ohms, part number 784-139, for 50W models.
- GZ34 rectifier no longer used.
- Cabinets have corner-lock joints with a quality control signature inside.
- Reverse (Black Flag) JTM logo used for half the year, carrying over from late 1966.
- Gold Plexigas back panel, changed from cream-colored.
- Dagnall transformers used in the JTM-100, changed from Drake.
- Chassis construction transitions from aluminum to steel in late 1967.
- First 200 Watt Majors appeared, with treble, bass and volume controls, active tone circuitry and KT88 tubes.
- White logo (changed from gold)
- The lip/shelve under the control panel is curved, changed from straight.
- Amp model prefix changed from JTM to JMP (Jim Marshall Products).
- The 200 watt Major was modified to match the normal panel layout and the active electronics where dropped.
- The output transformer turned 90 degrees in comparison to earlier models to reduce hum.
- Plexiglas panels changed to brushed aluminum startiong in early 1969.
- Larger black cabinet feet starting in July 1969, changed from small and gray.
The model number takes the form of four-digits preceded or followed by letter codes describing amplifiers characteristics. The table below outlines the meaning of these letter codes.
|Model Code||Model Type|
|S/ or S/A||50 Watt|
|SL/||100 Watt Super Lead|
|SB/||100 Watt Super Bass|
|T/||50 Watt Tremolo|
|ST/||100 Watt Tremolo|
1969 – 1983
Marshall amplifiers didn’t start using true serial numbers until July of 1969. The full identifier of these amps was initially comprised of a model code, the serial production number and the date code.
Letters were used as date codes to represent the year of production and this letter followed the serial production number. Letters B, I, O and Q were not used to avoid confusing letters with numbers.
|Model Code||Model Type|
|S/ or S/A||50 Watt|
|A/ or /A||200 Watt|
|SL/ or SL/A||100 Watt Super Lead|
|SB/ or SB/A||100 Watt Super Bass|
|T/ or T/A||50 Watt Tremolo|
|ST/ or ST/A||100 Watt Tremolo|
1984 – 1992
Starting in 1984 the date code letter was moved from the end to the middle of the production code, between the model code and the production number.
U 08177 1986 Model #2204S JCM 800 Master Volume Mini-stack Version
S/A V 10779 1987 Model #2204 JCM 800 Master Volume
S/A W 30626 1988 Model #2203 JCM 800 Master Volume
S W 29583 1988 Model #1987S Lead
1992 – 1997
In October of 1992 Marshall began using stickers printed with serial numbers and bar codes. These were comprised of nine digits in the format of xx-xxxxx-xx (though not always). These serial numbers can be decoded as follows:
- 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 being the first week of the year through to 52 being the last week of the year.
1997 – Present
In August of 1997 Marshall switched to their current serial number format which contains more information and is easily decoded.
These are printed on a sticker and affixed to the back of the amplifier and are comprised of a letter followed by ten numbers followed by another letter: A-xxxx-xx-xxxx-A.
- The first letter indicates what country the amp was manufactured in.
Code Country M England C China I India K Korea
- The next four digits indicate the year of production.
- The next two digits indicate the week of the year during which the amp was produced 01 being the first week of the year through to 52 being the last week of the year.
- The next four digits indicate the production number.
- The final letter indicates the voltage specification.
Code Voltage A 230 VAC, UK B 120/60 VAC, US C 220/50 VAC, Canada D 105/50/60 VAC, Japan E 220/60 VAC, Europe F 130/60 VAC, Mexico Z Speaker Cab
It’s important to note that, especially in the early years, Marshall was not always consistent — there are exceptions to these rules. Checking against other amps from the era as well as component markings (speakers, potentiometers, transformers) can help to confirm a year of production.