This is a used mechanical Backstay Adjuster that can be operated with any standard sailboat winch-handle.
It is made of chrome plated bronze and stainless steel and is in good mechanical condition, but there is very little of the chrome left on the bronze.
The length between pins can be adjusted from 25.25" to 33.75"
The pins are 5/8" diameter.
If you see this listing, the item is still available