It appears to be an old WWI prop which has metal leading edges to protect the propeller from their own bullets, as they fired through the propeller arc.
This early method of deflecting shots was a necessary stop-gap measure before the invention and widespread adoption of the synchronized gear, a device that allowed machine guns to fire only when the propeller blades were out of the way.
This method was a temporary fix and had drawbacks, such as the extra strain on the engine shaft and increased propeller weight, which negatively affected performance.