>>>>531 with Campy dropouts front and rear with a single eyelet. TREK is cast into the seatstay caps, but there's no bosses for shifters and the cables run on the top of the BB. The SR# is on the BB and is F1F6428 (the "F"s could be "E"s).<<<<
I suspect that MMs Trek is early '80s, but possibly earlier. The serial number thing still baffles me. I checked my Treks last night and here's what I came up with:
'81 950 - #017631 '84 720 - #128319 '84 760 - #130192 '85 770 - #109085
No letters in any of these.
On the '81, the SN is displayed laterally, across the BB shell. On the others, which use the later (post '83 I think) BB shell, the SN wraps around the edge of the shell on the drive side.
Wayne Bingham