It sold at auction for $1,525.00....

Here's what the seller had to say about it....

Description

This is an old 1930's pre-war airplane engine. There are
no identifying marks or names so I don't know what kind
it is. It is very large and heavy and has the original
propeller. It has a large exhaust pipe coming off of one
side and an old champion spark plug on the top. The
propeller spins with a very nice kick-back and a pop from
the exhaust pipe. It has some points on the back of the
prop that open and close when the prop is spun and a
couple of loose wires for a battery I guess. I do not know
about little engines like this and I did not try to get it
going, but it seems like it would fire up with no problem.
Its about the size of a large grapefruit and it looks like it
would be a very strong motor when running. I have it
mounted on a cool little metal display stand which I will
include in the sale. This was out of the estate of a 1930's
airplane buff here in San Diego.
__________________________________________________ _

A gentleman e-mailed him, and ID'ed the engine.