It looks like a wood carving swivel base/vise to me as well, but I think it's upside down in your pictures. You flip it over and use the two clamps to clamp it to the edge of a workbench and then you screw a piece of wood to the square plate using one or more of the holes provided. The piece of wood can then be quickly swiveled and tilted around as needed for carving, engraving, etc.
It looks like the round swivel pads have fallen off of the two workbench clamp screws, so if you try and use it as is the screws will want to dig into the bottom of the workbench top.