Now what are these?

[ChelleRee82]

These were in a box with striking wrenches. They are 1-7/8" Proto MFD USA, part number USN-530. On the side is stamped H.P. TURBINE Alloy Steel. They measure 2-5/8" high and have an industrial finish.
What do you think. An internet search turned up nothing. I think that the USN has to do with the US Navy and they do seem to be specialty tools. Almost like an adapter or extension.

 

[devoncoolman]

Looks like a socket u turn with a wrench. Most likely a special run for the us navy. Proto was probably contracted to make them.

 

[Wayfastwhitie440]

You said these, is there multiple sizes or multiple of the same size?

 

[1953mercury]

I would guess they are used for shaft nuts on high pressure turbines. APU units maybe. Mike

 

[ChelleRee82]

I have two of the same size, only slightly different in appearance and marked the same.

 

[ranw]

They remind me of these