How about correspondence from the original builder, checking the frame's serial number in his records? I lucked into a cosmetically wrecked but structurally sound Yamaguchi track frame a couple of years ago. When I sent it back to Koichi-san for refinishing, he identified it as the frame he built for Brett Reagan, a member of the US Jr. Nat'l team and the 17/18 pursuit champion in 1989 (his teammates that year were Mike McKenna, George Hincapie, JD Moffitt, Marty Nothstein and Jonas Carney). I understand that Mr. Yamaguchi built all of the team's track frames in those days.
The frame now sports the same graphics and decals that adorned it the day it first left his shop. Too bad the original finish was gone, as well as the parts. But at least I'm pretty sure about the provenance of the frame.
Dave Ross Portola Valley, CA USA
Proof of true team bikes may be very difficult to obtain, since many
such bikes were made in multiple examples and, of course, in most cases,
the groups, saddles, etc., they sported were also usually made in
series. In fact, several bikes may have been used by a given rider for a
single event. Engraving, special decals, etc., may be helpful, but these
can be reproduced.
The first form of evidence of a true "team bike" would be congruence
with known photos or other established examples of this bike-lacking
this, proof would be more difficult.
This would be followed by some form of provenance, e.g. a bill of
sale, letter, etc.,with a hierarchy of such provenance extending from the
bike's rider to the manufacturer, seller, etc.
George Hollenberg MD
CT, USA