Junk Descender Robot

This is a product from 40 years ago. It was a very unique product during the heyday of the figure-eight descender. It was useful because you could rappel with double ropes without them getting tangled.
It has been used considerably. Since it is made of metal, deterioration is minimal, but as it is a descender, we cannot recommend it for practical use. How about it for collectors of old mountaineering gear?
No claims, no returns, please.