The mid-1980's Cannondales didn't have CAD frame numbers. A 1986 Shimano 105 C'dale, for example, had a "3.0 Criterium Series" sticker on the seat tube, a "Shimano 105" sticker on one of the chain stays, the old "train station" logo on the head tube, a rock-hard Tange steel fork with a lugged crown, and a pretty nice paint job except for the usual corrosion bubbles around the mounting holes for the plastic cable guides on the top tube.

If this description more or less fits your bike, you've got a mid-80s C'dale. Its a great bike to be ridden hard, but worth very little in terms of money. I had one, put an aluminum fork on it and loved to ride it fast and hard for ten years.