G1 Serial #'S and Manufacture date

[TexBaz]

I was just wondering has anyone got a clue, as to how to determine manufacture dates on the G1 bodies. When I spoke to Nick, @ Kyocera (boy a what a trip that was) he seemed to be pretty vague about manufacture dates and serial numbers. He said something about a 3 letter code on the inside back of the body.
Can anyone cipher this 3 letter format.

Thanks😀