I can tell you that most reliable information is that Ernesto Colnago hasn't brazed a frame in decades - assuming he ever did. I feel confident saying that's marketing non-sense.

A photo would help on the other questions. The years you state sound early, but I'll know more with a photo.

Looks like they were 82-83. I saw an unconfirmed post that there were only 250, but I don't buy it - I've seen a few of them and they do come up for sale. I'd wager it was over 1000. They apparently do sell for a premium over other Colnagos, but they have an unusual seatpost - sounds like if you don't have the post, it's an issue:

http://www.classicrendezvous.com/Ita...go_oval_cx.htm