A really badly fitted one.

It's most likely a lever lock, I'd say non-curtain but I can't really see anything from that angle and with that light. In all honesty I only say that based on the escutcheon... can't make out a thing, there's something about it that doesn't look right to me though. Need better pics, taken straight on so we can see the actual keyway.
Assuming it is a lever lock, if you open the door and look at the plate it should tell you how many levers are in it. It could be warded with a single lever but those aren't anywhere near as common, guess it depends where in the world you are and how old it is though.
I wouldn't start off picking with whatever that is anyway. Mechanism aside, it's in a door. And that's a no-no.
