These were made by (some of) the same hands that built frames for Ernesto Colnago, but these went to SoCal and Marcel Calborne's shop. Looks like you probably have an SL frame, and the main clue will be the seat post size, plus your visual (and digital) check for rifling in the butted ares of the 3 main tubes at the BB shell. IIRC, the Colnago branded HS had some weird dimensions, closer to BMX than standard Italian road HS...