Where is the serial number? Never seen one with stamped chain stays like that.
Looks like a post-1981 Super or Mexico which had stamped chainstays, and were often half-chromed. Yours might have been overpainted, as the lug cutouts were often in contrasting colours, usually yellow or white.
In 1980 they started stamping the Colnago logo in the seatstay caps <tick> and the little dice-shape in the middle of the brake bridge <can't tell from photos>
In 1981 the inside of the chainstays got a long crimp on the inside to clear the tyre <can't tell from photos> and a Colnago stamp to the outside <tick>, the BB shell got the cable guides <tick> and the chainstay bridge became the little spool shape you have here <tick>, having been a short round tube previously.
With Shimano 600 Tricolor, which is a perfectly suitable match, and even with a bit of rust that's an absolute bargain - chapeau, sir!
Edited to add: Colnago frame numbers are usually non-existent for this time period. which is what adds somewhat to the mystique of 'fake' Colnagos, as a frame number database would clear things up in an instant. Generally speaking, if it's got the right cutouts and features it's probably legit. Unscrupulous sellers will sticker-up sometimes quite nice frames with Colnago decals but they'll only fool the naive, and there were a number of contemporary manufacturers who were 'associated with' or associated themselves with Colnago. In roughly descending order of legitimacy: Colner, Rauler, Saronni (the later Tecnotrat-built ones, not the original Colnago-built Saronnis which do have the right cutouts), Cornelo, Celo Europa, Vagacini, U Scannini, Loverdi and Martelly.
Torjus
