Deejay, I think that is a later Tecumseh, made in the US, not one of the Kirby ones. The Kirby ones have a very distinctive air cleaner, visible in the picture you posted. Unless SB went through a period of fitting some Tecumseh engines in the latter days of the 45, it may have been re-engined.
The plate on the engine states:
Tecumseh Products Company.
900 North Street, Grafton, WI 53024, USA.
I assume that is Grafton, Wisconsin.
It recommends OIL:
Summer SAE 30
Winter SAE 5W-30
