The Toyo revolving 4x5 back has a single lever on one side to ease opening the back, instead of a full bail, whereas the "reversing" back lacks the lever. The 8x10 Toyo back has levers on both sides. I can send you photos if you'd like, Doug.

Then, there are the backs that are held on with bailing wire. But, within this context, that's probably an anti-bail.