This thing is weird- almost like a screw shank nail. It's got a regular slotted head- so I assume it predates modern driver technology (philips, posi, etc) I've searched all over and can't find anything on the net anywhere. Weird. I couldn't find any markings of manufacture on the cabinet. So I wonder it maybe it's imported or something. But if it's imported, I would think it to be a more modern cabinet.
A reverse image search on Google brings up some more modern screws and other items, but nothing like this. . . .