Ratchet part?

[Hot Turkey]

Any idea what this fits? Its 3/8 and looks like it fit and old ratchet but I've never seen one like it.

 

[RTM]

Guessing it's a six sided shaft that fits in a hex bit driver, the swoop at the right end is for a detent so it doesn't fall out. The square end I think you've got figured out already.

 

[Zrxrunner]

Special oversize quick release impact socket uses those. I have one from Apex and have seen them from snap on. QR314 from apex. Think they have them in different size drives, which would justify having a 3/8 and 1/2 drive bits to insert.

 

[lu787a]

Looks like an E11.2 or 7/16" hex bit.