Nice antique iron clamp for a kitchen tool (cherry pitter, coffee grinder, bean slicer or similar?) or possibly for a farm tool (sharpening stone?). This came out of a farm estate here in Wisconsin, we found it in a lot of kitchen utensils, but are unsure of it's original purpose!
The screw turns smoothly and readily, and the clamp adjusts from about 1" to 2" open. It's not marked with a maker's name.