I believe it was a Continental R-670.

Forgot to mention that your picture is of a Gnome rotary engine, if I'm not mistaken...and I could be! (The whole engine and propeller spin on it's crankshaft, hence the term rotary and not radial.)

Oh, and to add further confusion, a Gnome rotary engine is technically a radial engine but the difference is a radial engine has it's cylinders mounted radially around it's crankshaft/crankcase and spins the prop via the rotating crankshaft,
whereas the rotary engine spins on it's crankshaft with the prop mounted essentially to the crankcase and the crankshaft is mounted to the bulkhead. Just some more useless info to know and tell...

And to add even further confusion, rotary engines, as we know them today courtesy of Wankel and Mazda, share nothing in common with a Gnome rotary. These engines use an eccentric rotor rather then a piston to convert internal pressure
to rotational force...sorry, I digress; time to shut up now.