Ok, here's another one from my family junk collector. Looks like a medical or veterinary device to me.
I'll see what you folks think.
Knob turns, adjusting the jaw.
The threaded portion forward of the knob has some sort of quick-adjust mechanism. Just flip the lever up, adjust by pushing in toward fixed jaw end. Lock lever, teeth engage threads allowing knob to really crank it down tight.
It's about 15 inches long. As you can see, it was a fancy nickel plated tool in it's day. Time has been rough on it.
Equine dental device?
Fancy pipe clamp?
Surgical instrument?