Knuckle Duster by Alexander McQueen. Brass.
Sizing is as follows. If worn on the right hand, correct orientation (see third photo):
- Index: 10
- Middle: 10+
- Ring: 9½
- Pinky: 9
It will be a miracle of all sizes match your fingers. The most critical for a good fit are the middle and ring fingers.
DO NOT TRY TO BOARD A PLANE WITH THIS. For real.