It's a thingey for clamping something that needs a gentle touch.
Wood workers and other craftsmen (and women) are very good at making something that fills the bill for what they need perfectly.
No idea how old....the evidence of wear will tell you that. But I believe it was something made for a specific purpose....

As Linda said: It's a home-made clamp for something the clamp user didn't want to scratch.

The size will set certain limits on what would have been clamped ... perhaps small veneered box tops?

Its a home made wood worker's clamp. General purpose use one being to clamp pieces together while the glue dries.

It's a carpenters door stand..A door is turned over horizontal then one end is slipped into that stand to hold it vertical while the carpenter mortises the hinges.

Here is an illustration I just made to show you how its used, Although they do commercially make door jacks, generally each carpenter makes his own so there can be all different variations in the design.

Thanks, Pup! Makes perfect sense to me. Probably of no particular value, then, unless it's really old. If the screw was wood, that would be a different story.

Regards,

Jim