It's a 'Universal' vise. Was one of the first Rotary vises made. The one I have works great. Maybe there's a 'User Manual' somewhere on the net. I think I saw that a very similar model came out about 3-4 years ago. Not sure who made it but when I saw that model, I only caught a quick glimpse, I thought it was the same as mine.
The thumbscrew on top enables rotation. There's a screw below it that adjusts the angle. Open the lever and the round screw on top, close to the head of the jaws, adjusts the opening width. Leave opening just a smidge larger then the width of hook wire. Put hook in and close the lever. To remove hook, simply press the button on the top next to the adjusting screw. Oh, and the adjusting screw should not rotate easily. Not a 'full' rotary but an excellent vise.

Allan