there were a few bikes at the time that used bolted rear triangles to keep clearance of steel at the rear and allow an alu front triangle....nishiki, mantis, cr7 etc....was the bonty one a flex plate bolted into the bb? non production iirc?
its a shimano r650 ....longish 57mm reach shimano. drilled out rear of cluster fork to take the sunken allen nut but had to use the long version. pretty reasonable brake, though a paul racer would have been nicerer....
san marco magmaa....magnesium alloy base tends to snap across the saddle just where the nose starts to widen out to the rear....good other than that....
sweet as.