I'm guessing they're for some specific application, the plugs are pretty short. It's interesting they have the hole, that's usually to allow you to plug another plug in to that connection. I've never seen that exact size & shape before.
No spring thing on the pin, like a banana plug has. The hole does look like its for another plug, but not much clearance. Without the corresponding female socket, their of dubious value. You could measure the pin diameter and then search for an answer.