I just purchased a bike today, but can't figure out what brand it is. It's been painted and all identifiable markings and stickers have been removed. The rear derailleur says 'Shimano 200GS' and the crank arm says Fuji, but I'm pretty sure neither of those is original. The best hints are the head tube, which has a pretty unique pattern on it, and the stem shifters, which have "FINGER TIP" written on them. No braze ons for water bottle if that helps date it at all. 6 speed freehub, but not sure if that is original either.

THE S/N appears to have two letters and then 6 digits. Can't read the letters, digits are 124318.

Thanks!