I've got a "Whatzit" for you...
It came in the box with the second hand Omega D-II enlarger I got from my uncle.
I thought it was a negative holder but, when I was packing things up to put them in my car, I really didn't spend too much time thinking about it. I was more worried about packing things up and getting them home without breaking anything.
It wasn't until I got everything home and started sorting it all out that I gave it a second thought. It certainly seems like some kind of negative holder but it doesn't fit the stage on the Omega enlarger.
Anybody have any ideas?