I think you're right. Looks like a multi-angle l-bracket. Out of shot, some had a catch with three angle settings. Think it had a tilt setting on the cold shoe too.Heck, just an old school flash mount?
You might be able to use it as a screwdriver, but it doesn't fit a slot well nor was it designed for that. Some didn't have the angle bracket either, but the better ones did. This one does have a hinge, but some did not.I'm pretty sure I had this in my hands, and maybe even tried to use the end part as a screwdriver (which of course is not what it was designed for ).
Just know the shape, probably there is hinge on the right? Maybe I still have it in my barn, but what is it...
(But I've never had the angle bracket though. )