I have this random part in my stash and I think it's for a clock.  It is very solidly made (heavy for its size), so I want it to be used again.  Outer diameter is 4.25", inner diameter, where the threading is, is 4".  Inner threading, threads are 3 mm wide.  Curved at the face with knurling detail around the sides.  Heavy and solid with lots of surface scuffing.  Can be revived by polishing and you can make it any color with Rub N- Buff.