From a history of Colnago frames: (emphasis is mine)

"To even confuse things further, also in 1980, a new Nuovo Mexico (catalog name only, no label on the frame) model was started using the crimped tubing at top and down tubes. These new Colnago Nuovo Mexicos had nothing to do with Merckx but more to do with the beginning of experiments with crimping and tube shapes which ultimately will result in the Gilco (GILberto COlombo) tubing with Columbus and should be considered the first of their own kind. Guiseppe Sarroni should be associated with these Nuovo Mexicos since he took them to victories. The Nuovo Mexico with anti-vibrant fork is not to be confused with the Profil (1982-1983) which has a main triangle with all tubes crimped with CX fork or the Profil CX (1984-1985) which is the same as Profil (all main tubes crimped) but with aero shifter bosses on the top of the down tube. To confuse the matter even further, the old Mexicos were still being delivered into the1980s due to Colnago's notorious delays in filling orders on time or frame sets languishing in bike shops for years before being sold.

Basically the Merckx Colnago Mexicos (1974-1979) had round superlight main tubes, Sarroni Nuovo Mexicos (1980-1985) crimped top and down tubes, ESA Mexicos (1986-1988) had 6 ribs on main tubes, Zoetemelk Mexico SR/CRs (1985-1986) had a crimped top tube with a 4 rib downtube. "

OK: My bike only has crimped top and downtubes, so does that make it a Sarroni/Nuovo Mexico. Or, because it has shifter bosses on top of the downtube, is it a Profil CX which should have "all main tubes crimped".

You guys know more than I...have at it.

BTW, the black Gyes leather saddle (chrome rivets and center cut out) is now mounted on an Origin8 350mm seat post, and I got the XL toe clips onto the pedals. Took a spin (its 34 degrees here today-Freezing) feels great.