To clarify further, your bike is the 7,655th "frame" build after the introduction of serial numbers. Simplex didn't pay too much attention to frame & motor numbers. They build the parts, numbered them, then put them onto the shelf to await assembly (or sales thru service parts). When it came time to assemble, they just grabbed the closest one to them & slapped them together. That's why the frame numbers which are near the beginnings or ends of the calendar year are fuzzy....they might have been grabbed in December or January & no one minded.
Another complication is that any unsold bikes from one year were just sold as the next year's model (like lawnmowers, etc). I read somewhere that there were a lot of left over '57's which got sold as '58's. Kaiser Frazer did the same thing in '52/'53.....they just re-tagged the left over '52's as '53 model cars.
Mike Sal