The 1st TWO LETTERS of the Serial number are the indicators for the Year and Month manufactured. The decoding information is in THIS THREAD, "PIONEER Dates of Manufacture" in the sticky section at the top of the forum 1st page.
As a point of reference the PL-600 (Direct drive ) was built between 1979 and 1982 for the 1980 to 1982 model years. (Model Years start in Sept, and end in Aug.) Production started earlier in the physical year to build up stock and to carry out logistical support for the model year.
If you want to date a turntable, that is your business. Sure, if things start to get serious, it might be an issue. But if it is just a date or two does it really matter?
If you want to date a turntable, that is your business. Sure, if things start to get serious, it might be an issue. But if it is just a date or two does it really matter?