Dodecahedron Case back opener..

Is there a specific brand that these are all from? Modern or vintage?

Usually with stuff like this it's brand specific, both with the shape and the size required.

It might also help if you let use know what sort of case opener you have now. Some openers have inserts that are flat and are meant to go on two opposing flats on case backs like this. I've never really trusted this design for opening these though, as I feel it could slip too easily.

I use the Bergeon 5700 opener, and on that I typically use urethane friction dies that are non-marking. It's rare that I can't open up a case with these:



The most common brand I service with the style of case back you are referring to is Panerai, so I have a full set of Panerai case back dies for the 5700.



Cheers, Al