What is this? Hydraulic fixture or work support?

[bartels_metal_works]

Trying to identify this hydraulic component. I ended up with 4 of them at an auction, expecting that I would be able to figure out what they are... The best I can come up with is some sort of clamp or support for use in on a fixture table. I have not attempted to actuate it yet, I suppose I could try with just air pressure. With the port slightly off-center, I wonder if it rotates, or just extends.

 

[jack stand]

Connect it to a hand pumped "Porta power" and see what you get. I think your guess is a good one.

 

[cvairwerks]

No exit port visible, so probably a clamp.