Wings that control light -[ SoS ]-

A two-bladed shutter from a Simplex X-L 35mm motion picture projector. I've seen them called “two-wing” shutters, which makes sense considering the conical design.

 

As this shutter makes one revolution per frame of film, one blade (or wing) blocks the light from the source while the intermittent movement advances the film one frame, then the second blade creates another flash for double the perceived frame rate, minimizing annoying flicker.

Done