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...I dimly recall reading something about these in some dingy corner of the internet, about the contract builder, but I can't find it. Which is no big deal, because contract built frames that are not credited are sort of par for the course from this period in Italy.
If you look here, you'll see that for about the first ten years he owned the company, Colombo was trying to steer it in the direction of more American market share. I think this frame is from about the end of that, when he finally decided the real future of the company lay in going for a more high end, exclusive nature, and all the art philosophy started showing up in their advertising. Anyway, there's nothing at all second rate about Cromor tubing, IMO. I have several frames made from it, and I can't really say it makes a difference in the way they feel or handle on the road. They just cost a little less to make and buy at the time. Yours has a nice mix of components, but if it doesn't really fit you, I wouldn't think twice about stripping them off and selling on the frame.
Frames that almost, but don't quite fit you are vexatious things to have around.
^^^sometime around 1979 or 1980. Note the variety in the product line.