I purchased a Sherpa last year with the intention of restoring as I have done a fair few in the past. I am just looking for a little advice as to the definite year/model as there are a few things puzzling me. To start off the bike is sat in a frame believed to be SM but can not confirm, the original frame is supplied which is numbers matching to the engine.  Engine JM-19906685-A Frame JB-19906685-A The Number of the frame the bike is currently sat in is 685, no letters just the th