Early Nuovo Record derailleurs were marked patent only(1968&1969). I think PAT 70 is the earliest non patent I have seen.
I believe the Colnago Mexico on EBAY is about 1982 not a 70's model. I had a late 70's Super I bought from Mike Kone in 1980, it is quite different. The one shown has COLNAGO stamped in the right side chainstay just behind the rings, I believe they did this in 1981-83. I remember a friend bought one like this after riding mine when I was in Grad school. The workmanship is much more mass production with no filing at the rear dropout to stay junctions.
ZZ From: Roadgiant@cs.com ZZ Date: Wed, 28 Nov 2001 02:58:20 EST ZZ To: classicrendezvous@bikelist.org ZZ Subject: [CR]Colnago Mexico ZZ Hi all, Can anyone tell me about a Colnago mexico with eyeletted ZZ ZZ dropouts Was this bike intended for touring with fenders? Would it ZZ have had the 'mexico' components of Colnago pantograped Campagnolo ZZ parts? What years was it built? The frame in question seems to be ZZ ZZ a '78-'80 judging from the Colnago engrave seat stay cap, yet both ZZ dropouts are Campagnolo.