Yea, this is a repeat discussion on some of the facebook groups, but people need to research this because there's functionally no way they actually used these for the actual props due to the fact these things are solid, brittle bricks of material that are meant to get worn away in a motor. While the overall prop design is uncanny, the props themselves very likely were scratch built and inspired by the motor brush
thank you... its like beating your head up against a wall