Wrench set for threaded rings with four slots in the faces - used in camera lenses and the like. Usually you use a spanner wrench for that, but these thingies look like they're made to grab three of the slots, and then use the bar to turn them. A kind of guess, but I've worked with plenty of these rings, and they sure look like they'd do the trick. They have an automotive look - maybe for bearing retaining rings? Special auto ****** parts?
I know the rear end gearset of some motorcycles (BMW's for instance) have such a retaining ring.