Originally Posted by machinist42

There's a FB Group started by Ron Cooper's son where you may find further information or not. Some of the opinions there are ill-informed, especially regarding serial numbers. Cooper used a 3 (three) digit serial in his early years and when he reached 999 every three or four years he'd simply start over at 001. Later there could be no serial or in your case a 4 digit? (Is there a corresponding number on the underside of the BB shell?)

He used whichever tubing was appropriate or at hand. You may want to scrutinize the tubes for stampings and check the steerer for "ridges?" Found a "Super Vitus" stamping on the inside of the fork's blades on our Cooper, which probably is from the early '70s. The stampings can be very faint and well nigh indiscernible to the naked eye.

Cooper made great bike frames freehand and don't think he gave a rat's ass about what his customers hung on it. There is abundant information about him out there if you are interested, and he was interesting.

Classic Rendezvous is another source of information for you, and though your bike is probably from the 90s, he is considered a consummate KOF and hence mention of his later work is entirely "On-Topic." Some folks there really know their stuff.

Congratulations on your acquisition!