I was given an old bike and have started to completely disable it. After removing the rear wheel I noticed the hub flanges looked quite different than a normal hub. Instead of a single hole there is a hole large enough to allow the spoke head to pass through and there are slots on each side where two spoke heads are held. Here is a drawing I made to illustrate what each spoke anchor point looks like.

It's very obvious this allows any spoke to be replaced without the need to remove the freewheel. I find myself wanting to put this hub on my touring bike! Anyone else ever seen anything like this?