This is a Beta recreation of the miniature Torpedo enemy, Torpedo Bill.
Within is ExGFX62 which rocks back and forth like my Bullet Bills, AND ExGFX63 which only the propeller moves. There is also a simple test level AND they are interchangeable. When inserted just switch between 62 0r 63, whichever you prefer.
Note: ExGFX62 can be as a skin for Russianman's Mini Torpedo Ted, found here