Mamiya Universal Press camera back adapter plate so you can latch whatever you want onto the back of your Mamiya. I'm still messing with the FFD on this puppy, so I'll update if I get a thickness I like better.

I've got a few instant film backs in the works, so stay tuned if you're into that kind of thing...

If you're medium-format-curious and/or open-source-camera-curious, the Mamiya Universal is a dope place to start. They can be had pretty cheaply, and one of the big selling points of the camera was that they were designed to take all kinds of different backs.

Something potentially useful to know about the Universal is that there were a few lenses designed specifically to hit a large area on the film (good, depending on what you're planning on sticking back there). Made to work with Polaroid backs, the Mamiya-Sekor "P" lenses will do you right if you're getting vignetting. The 127/4.6 is better than the 75/5.6 for this.