This is a 120 film back that takes 12 6x6 pictures. Fits on a 4x5 camera with Graflok back like the Speed Graphic or Crown Graphics, or other international back cameras. I haven't used it, but seems to be in good working order.
Interesting. It's been years since I last used my roll holders and didn't remember an internal mask in the 22 holder, but a quick web search shows several backs for sale with such a mask.