Very Odd angle plates, purpose?

2 photos with scale. No marks, shop made? They are almost identical. I’d especially like to know purpose of the little nut-and-bolt-looking affair in a hole near the base of each. These seem to have been used in the grinding department of MM Tool and Die, Littlestown, PA, auctioned off last year.

Looks like shop made tooling that was dedicated to a repeat job that was a PITA to set-up/use standard angle plates for. Are they hardened? I was a tool and die maker in a former life and I don't recall anything "common" from prog dies that these would have been useful enough to spend time making them. It looks like whatever they were used for might have been "L" shaped with the inside of the "L" being the reference surface and one leg going through the ovoid cut-out at the bottom and one side referencing the rib on the plate(s) for perpendicularity. I'd be surprised if these are finished on anything other than a mill as some of the surfaces look like it would be difficult to grind in and still be planer/perpendicular/parallel with any real accuracy. At first glance they look like they were used for milling. Then again, it's my first cup of coffee and I'm up way too early.

I vote shop made for a specific job. I have an angle plate I made a bolt/dowel pattern to match at 4x 10deg increments with a matching block with a 5deg angle on one side and flat the other side. I worked at a stamping place where we ground so many angles for shear and such it came in real handy. I also have a shallow V block (30deg I think) that I can attach to the angle as well for round pins/punches.'

Shop made, yes, but they seem too "universal" to be job specific. They are an uncommon design, but were made to be used for a lot of different types of things. Look at all the working surfaces, holes, and different orientations in which they could be used.

I'd bet they were an apprentice project. A simple tool redesigned to make it more of a challenge to make so it requires more skills from the maker.