Looks like a Suzuki B100 engine...the S15 at the cylinder base is indicative. The engine will be a 2 stroke and any info will need a year of manufacture....usually on the steering stem. It looks like it needs a lot of work which is to be considered as it wont be worth very much even in pristine condition.
This may be of some assistance.
From the Suzuki Two Stroke Message board.....
According to the " All Suzuki's Ever Built Site", there is a 1965 B100 with no oil pump or tank. It was known as the B100. In 1966 the bike went to oil injection and was called the B100P. The P designating Posi Force. The metal tag with the frame and engine number is riveted on the frame just ahead of the right rear shock. My 68's contain the B100P designation on the tag. The frame and engines are only stamped B100. The frame vin number is stamped just to the bottom left of the oil tank. The engine numbers are stamped into the top of the case on the right side of the engine, towards the outside of the case where it meets the clutch cover.
The throttle cable would also have only one cable going to the carb if it wasn't oil injected, not a split one that would also do the oil pump.