Originally Posted by bulgie

From the fender boss in the chainstay bridge, we can tell it's not a racing frame. That leaves two possibilities: (1) a Discovery, a small-batch production model, or (2) a Signature, which was the informal "model name" we used for custom (one-off) frames. Note, many of the production models such as Impulse, Challenge and Disco, also got a decal with Bill's signature, so that feature doesn't make it a Signature. Sometimes the production models didn't get any decal telling you that. If you find that frustrating, join the club. It did bother me that they didn't use serial numbers, which seemed lazy and unprofessional. I never did hear Bill's reasoning for that, probably just "how I've always done it". Funny story, at the previous shop I worked at, I put a serial number in each F&F I made, until the owner made me stop! I didn't bother trying to fight for serials at Davidson because by then I was tired of that fight.

A Signature could be almost anything, including a near clone of a Discovery, which could make it hard to distinguish. But whether a frame was custom (for someone else) or not means little to the future buyer of a used bike. The one worhwhile thing you might get on a Signature is Prestige tubing, or Columbus EL, or any of a number of fancier tube choices than the non-heat-treated Champion tubes on the Disco. But Champion is a very good tube, so nothing to be sad about.

If you care about knowing who built your frame: Disco, Challenge and Impulse originally got forks and rear triangles that were fully brazed by Tange in Japan, to Bill's spec. The rears came with the IC seatstay tops that were faux-pantographed with the name, as shown in the photos. BTW, the name was cast in, not pantographed if you want to be excruciatingly correct. Earlier customs, late-'70s thru maybe '85, had actually-pantographed seatstay tops, rounded on top not pointed. Those were only on customs.
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