Can you document that, including the frame details? The Nuovo Mexico was succeeded by the Essa Mexico in the mid-late-80's. Check the '88 catalog on bulgier. Some of the tubes on the Essa Mexico were fully shaped, rather than just having the channels on top and downtube. By the time that paint scheme rolled around, the frame details on that bike (Colnago stamped in the sides of the stays, bottom bracket style, seatstay caps) had morphed quite a bit. By sometime in the early 90's, Colnago had switched from "Colnago" on the caps to a single clover. The details on this frame all point to early-mid 80's, unless you have some real evidence to the contrary?