Curiouser and curiouser.
My 1971 JS II
In addition to me just being flat out wrong I see two possibilities:
The cavity shape did change over the life of the S-100.
The JS and S-100 bodies are not as close to identical as people claim.
Perhaps this was a JS body mated to a guitar neck?
62452 seems to be the serial which puts the neck circa 1972 but unless Hans has something, we will not be able to identify which model.