Technics have been putting serial numbers on their SL-1200 and SL-1210 turntables right from release in 1972 (1979 for the Mk2). This serial number contains the year of manufacture and in some formats the month as well. It will be a 10 or 11 character serial number consisting of both numbers and letters and is located on a sticker on either the bottom of the deck or the back. From 2008 onwards an actual full date is stamped on the tonearm base cover. Please note that this should work for all revisions of the technics 1200 and 1210, if you have a Mk2 (by far the most popular model) then you can ignore any dates returned that are before 1979. You can enter more than one serial number by separating them with a comma. If you get unexpected results please double check all the characters, in particular the letter S and number 5 can look very similar.
Technics serial number :
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If this tool fails to return a result or you disagree with it please contact me. I will look into it, attempt to get you a date and then fix/improve this tool.