Use and design.
Ancient but still in use.
I'm not sure the handle is actually square... the handle end is square, but that's to retain the head.Why square the handle?
It might be, I tried to enlarge the picture... we'll see if it worked.More often oval in section...
If it is what I think it is it is part of something called a stitching horse. I have built one. It is used in leather craft. I believe they are typically mounted to a chair/bench affair and that whole assembly is called a stitching horse. The leather is clamped in the vise and the awl/needle and thread are pushed through the leather. Usually the jaws of the vise are positioned on the seat so that if you leaned ahead your nose could be tightened in the vise from the sides. The lower pic shows the base going off to the side so I would assume it is designed to mount to a workbench or something instead of mounted to a chair. I built one over 30 years ago and it is still used by the owner several times a week.test 2:
this device had a lot of antique dealers stumped on an antique show I watched.
any guess, bit harder than the last. be obvious when you know.
here is a modern one with dimensions;
Click below to see what I based the one I built on. The one shown only had front legs and I thought it was a bit silly to have to use a chair so I put legs on the back too.