I think that around about that time Jim Hopes were the silver grey 1st cable brake, I think it was after or a year or so the black versions came out. Might be a bit of info to be gleaned out their history bumpf.
Cable brake seemed to disappear off ebay etc about 3 years ago. But likely many here own them and a general ask might produce some.
Silver mayb 1990/91 and the black ones that looked like they werent beaten out by a blacksmith were '92-92, then C2's began their development. I think they came out 93 or 4 :? As i had new C2's fitted in 96(front only, sport hub) and formula were the current ones :? I got the C2's cheaper as they were older kit.
If you want something to put a rear on, ive a spare !S mount of the type that is the cut down hope hub axle, bolt on thingummy. etc
Outside of that period hydraulic you're talking the No2 system, which though about can be hit or miss operationally. The IS molunt works and fits the same but offers a wider option .
If youve no mounts. Sorry, forgot to ask which bike. I tracked back a few pages but i couldnt see reference to it.
Incidentally, if youre thinking the early formula as an option, dont. They fade horribly.