You can use this tool to find the manufacture date of any Boss product (as well as the very early roland pedals). This includes guitar effects pedals, multi-effects processors, drum machines, tuners and metronomes. Boss serial numbers are either 4 numbers, 6 numbers, or be 6 or 7 characters with 2 letters and the rest numbers. If you have a code with just one letter please double check in case another character is actually a letter. It isn't always next to the other letter. It works by first decoding the date code part of the serial number, then because the date code on Boss devices was repeated it will be compared to my database of Boss product manufacturing dates to narrow it down to only those dates when the unit was being made. To get the best chance of getting only one date returned it is best to enter your model number in the second box.
Boss have used four formats for the serial numbers on their guitar pedals over the years. 1977-1981 (4 digit), 1981-1989 (6 digit), 1989-2010, and 2010 to date. This tool supports all formats and if available a link to find the value and a PDF manual will also be returned. Some examples :-
For details of my Boss pedal database click here. For Roland products please use the Roland decoder as that has the Roland production dates.
You can normally find the serial inside the battery compartment or on a sticker on the base.