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Old 01-14-22, 05:05 PM
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Road Fan
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Join Date: Apr 2005
Location: Ann Arbor, MI
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Bikes: 1980 Masi, 1984 Mondonico, 1984 Trek 610, 1980 Woodrup Giro, 2005 Mondonico Futura Leggera ELOS, 1967 PX10E, 1971 Peugeot UO-8

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Originally Posted by T-Mar View Post
That's the Reynolds 531 Butted Main Tubes decal. From what I understand, that is the Trek factory serial number format for the 61x series, though the year code doesn't follow the normal system, which complicates exact dating. Given the presence of top tube brake cable clips, I'm assuming it is 1981-1982, as these catalogues doen't show the models, but the 1983 catalogue shows brazed-on top tube cable tunnels. Both the 613 and 614 appear to be identically spec'd for the crankset, though neither are triples, as on your bicycle. Hopefully, some of the resident Trek experts can provide further information or correct me if I'm wrong. Treks really aren't my forté.
I don't agree that the dating is complicated from being as good as it can be, in this numbering system. This number system gets you to the month when the frame was stamped. After frame build they were often racked until needed for deliverable bike builds, so the released (painted and equipped) model year could different from the frame stamping date. It does keep you from using the build sequence chart where you can see where in the sequence if 21"" frames it sat.

It seems they had both systems running at the same time (I don't know if that means anything). My 1982 720 is numbered in the 6 digit numerical sequenc, as is my 1984 610. I can see that my 720 is one of the first ones to roll off the line. This bike, a 1983 610 frame, is numbered in the older alphanumeric system, whicn I think dates back to the 1970s frames.

Last edited by Road Fan; 01-14-22 at 05:31 PM.
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