I’m always entertained when I stumble across strange vintage femdom pornography. Often it’s terrible bondage or odd outfits that catch the eye. In this case it’s an unusual means of torture.
I think the original form of a thumbscrew was a small vice, that crushed the fingers. The domme here seems to have taken the screw part of the name a little too literally. I’m guessing these are woodwork and metalwork tools that have been repurposed by an inventive pornographer. She at least seems to be enjoying herself, even if the slave isn’t.
I’d guess from the color and style this was originally shot in the 1970’s. It was recently posted to Twitter by mrunderheel.