I got this mixed in with a whole lot of wrenches - I've seen this before,
but darned if I can remember on what - *I don't think it's automotive,
though it could be. it is presumably held in place with 1/2" diameter bolts,
forged, marked DF and DD57 some silver paint residue and some little bit of
red paint - what does it fit?

It looks like some of the ones my brother makes out of cheap taiwanese
wrenches by heating and bending, or sometimes cutting and rewelding,
to save the exhorbitant cost at the parts counter or traveling tool
truck, for working on diesels (Cummins, Detroit, Dresser, etc.) in all
the weird places they have to access: injectors, push rods, all
that...