Yes. Its an S.M.
These came out in 1980 and you dont see them very often.
The ones I´ve seen before this one all had a TP-6 tailpiece, but they might have come with this one aswell (or somebody has changed it)
Maple neck, dot inlays on the fretboard, belly carve on the back, and no binding at the back of the body. Tarback pickups.