The rearsets on this particular Rickman are from a Laverda Jota. The bike was originally built in the mid 1980's by Lance Weil, aka "Rickey Racer." He was one of the earliest American privateers racing in Europe and later became one of the foremost Laverda experts in the US.
Weil died about three years ago as the result of a shop lathe accident.
Standard location for the caliper is on the right side, but the orange Rickman has it reversed. Since the Rickman speedometer drives from the rear hub, reversing the fork tubes is easier.
BTW, the right side oil tank cover on this bike is cast aluminum.
RR