don't know if Liberia was building FR bikes in the '80s at all but with BSC BB threading? it seems to have very thick paint which may hide some clues, would help to see what else is on the BB shell besides R2 or even if I read that much correctly. The "web" in the backside of the seat lug slot was a clue for some other frame ID, but cannot recall details, now, otherwise the only other small clue of note is the head lugs have a small point on the fronts which also could be helpful...but not to me. Do you know the seat post size?