Marshall dating serial number
Note: "A" Date Code: The "A" Date Code ran for 18 months (July 1969 - December 1970) so the "B" Code was not used.
1979-1981: Some Marshalls made from 1979 to 1981 have the serial number on the front panel.
This clearly is when the component was made and not when the bike was made, but unless the component or bike manufacturer had lots of stock lying around in inventory, the date should be a fairly good indication of the year of the bike.
At least it would be the earliest date that the bike could have been made.
In the early 1960s Jim Marshall was a drum/percussion retailer in Hanwell, London. Fender amps were popular but expensive and Jim thought he could produce them at a better price. The main difference was he used four 12 inch Celestions in a closed back cabinet vs the Bassman’s four 10 inch Jensen speakers with an open back.
Initially using US amp parts he switched to UK components to save money.
Of course, all this assumes the bike has the original component.
The most likely components to be original are the stem, handlebars, seatpost, and brakes.
The earliest Marshall amplifiers were made in 1962 and had no model or serial numbers.The switch from 6L6 to the KT66 valve gave Marshall amps a more aggressive tone.Eventually the KT66 became too expensive causing the jump to EL34 and even more aggression. [Source: Wikipedia] Dating Marshall cabs and amps Info from Wayback Machine Serial number (no barcode) version: Marshall Serial Numbers and Chassis Codes Does it have a serial number stamped on the chassis?Early Marshall through the JCM800 series July of 1969 Marshall introduced the date coding system.Some of the older amps have an inspection sticker on the top of the chassis and they usually have the day, month and year the amp was made or inspected.
From July of 1969 until September of 1992 the date code system included a letter of the alphabet in the serial number.