These are called "Zwerg-Stecker" and "Zwerg-Kupplung" respectively in German, but I've never seen them anywhere else. It basically translates to "dwarf plug" and "dwarf socket".
It is a 2.6mm mini banana plug system, I remember seeing them on some lab equipment in Uni, but never seen them anywhere else. We use banana plugs quite often, whether it's 4mm or the smaller 2mm system. Unfortunately, making cables ourselves it sometimes a bit of a hassle, since they're more or less designed to be pre-confectionated wires. Now, I was thinking of introducing this Zwerg system, since it is designed to be not confectionated at all. Except, you're supposed to cut your own wires and put the plugs on it.
It has a weird size, though. 2.6mm and a very short plug. I haven't seen complete cables made with Zwerg plugs, but I have seen them quite often in lab equipment, where people would make their own canbles due to various lengths, etc...
I don't know the manufacturer, I've seen them in a couple of electronics stores, but that's pretty much it.