Phantom Transposition Three Pin Brackets for glass insulators. They would mount to the side of the crossarm and use one of the crossarm pins for the fourth pin.

All brackets have wood cobs on the steel pins that are in good shape.

I have three available for sale. Asking $35 each plus shipping.

These are heavy, I'm guessing around 20 lbs (each) with the three insulators. If the insulators aren't wanted on them would be around 14 lbs (each)