I have a Colnago Mexico frame, creases along the top tube, down tube and inside the chainstays, Colnago stamped on the top eyes and chainstays. It is NOS and has never been built in a bike (Just had the headset and BB fitted). It was bought in 1983 (not sure when it was made), the rear drop outs are spaced 130mm and have never been altered. I would say it is the same frame as M Poore bought on ebay recently and I would suggest that his has been resprayed but not re spaced. Mine will be looking for a new home soon (57cm), contact me off list. I would put a price but have not really though about it. There is another Colnago Mexico full bike on sale on ebay, but this looks like it has been resprayed as only the chainstay is chromed and not the 3/4 rear triangle.
Regards
Martin Coopland