I have a 51cm uncrimped Mexico with the same chrome Mylar chainstay protector. Mine has top of BB cable guides, 2 toptube brake housing guides, DT shifter braze-ons and water bottle bosses on the DT only. The only real chrome is on the fork crown (maybe the dropout faces, I can't remember here at work). Mine also has recessed brake nuts. Looking at the 1979 Colnago catalog, the difference between the Mexicos and the Supers of this vintage was that the Supers used Columbus SL and the Mexicos used a lighter gauge Columbus Record tubing. Personally, I think the uncrimped Colnagos are much more pleasing to the eye than the ones with fluted tubing. BTW, the newer chainstays weren't pantographed, the Colnago name was stamped into the tubing.
Kevin Ko
Eugene, OR