Unknown tool. socket?

[1stkam]

Again I ask your assistance. I have no idea what this is or where I got it.

 

[Stadger]

The tightening/loosening part of a vise?

 

[Richard Cranium]

my guess would be some kind of spreader, you are missing the two threaded pieces and have only the cap.

 

[kctyphoon]

I doubt this is it - but it almost look like an endcap that would be on the screw of a vise. Looks like a sliding handle could go through that thing for leverage on tightening a vise of some sort..

Purely a shot in the dark..

 

[L.Cheapo]

Transfer tube mount?