Strange York 209...WTF is this thing

So I recently acquired a York and after inspecting the crank shaft it's for sure a 209. It pumps well and would make a great EDC I'm sure BUT...this thing is strange. I've never seen a York like this. It's unfinished for one thing which I guess someone could have just stripped it. However, the oil check holes in the sides of the cases that every York are supposed to have aren't there. There aren't even any provisions for them. Their actually located on the back of the compressor. Also the rear cover which should have 4 bolts holding it on are actually several flat head screws. This thing is supposed to be the completely stock unmolested pump off of an early 60's mercedes but I can't find any info on this thing at all. No one I've asked knows anything about it. Is it some rare pump that I shouldn't sell to someone that's going to use it for an air pump?? Any info would be great.


In this last pic you can see the weird screws holding the back plate on and the oil add bolts on the back of the pump instead of the sides.