Actually, those darned '80's Schwinn serial numbers are usually a bit difficult to decipher it seems. But for '80's Schwinns, if the serial number starts with "S", has another letter for the second character, and then has a number after that, it's likely (but not positively) a Greenville-built Schwinn, with the "S" indicating Greenville, the second letter indicating month of frame manufacture, and the next character (a number) indicating the last number in the year of manufacture. Example: I've got two le tours (an '83 and '84), serials starting with SF3 for the '83 (frame manufacture likely in Greenville in June of '83), and SG4 for the '84 (Greenville, July, '84)-