Hi Picchio, from "squadcar" a former principal at Proteus we found out this bike was done by them. There isn't nearly enough information about the Proteus bikes, but they were huge in creating the modern era of artisan framebuilding in the US.

Those are very definitely Cinelli lugs and I'd gone with the Cinelli theory for awhile (particularly for insurance purposes) but it'd be like the one bike in 40 years that didn't have the trademark fastback seat cluster. The steerer tube is stamped "REYNOLDS 531 BUTTED 16/13" which would certainly rule out Cinelli origins.

I'm sorry to have not updated this thread, but it had been ignored enough I forgot it too.

What got me curious about it is the need to overhaul and refinish it. If it remained a mystery bike I would probably have done it up rat rod style in red primer but now it's got a provenance and needs to be done proper like. Anyway, I'm blogging the rebuild if you care to look.