I came across this a few days ago, and I can honestly say that I've never seen anything like this. Sorry for the blurry picture, but to better describe it, the only path for a key to enter is curved like a half circle. I've browsed many different locksmith forums, as well as general search engines, and can't find a thing.
You're close. Most people call them half-moon keys. In your case they're not true Half Moon because of the bit in the middle that is also missing. These are an older Abloy design from their Profile or Hi-Profile line. Baton and LAI make generics now that the Abloy patent ran out for that keyway and that type of mechanism.
The big rectangular lock body the core is installed in is called a T-Handle. It pops out and then you turn it a bunch of times to unscrew it in order to open the door.
a company called ESP also makes these vending hardware abloys, that one is on a vending machine.
in my opinion, the blockout of the center of the keyway makes this particulary harder to get tools into. that area is where the tool for a half circle abloy would be.
