Those are interesting contraptions indeed. They're also known as key caddies or keychain spiders. I know there are a few of those out there including this wenger (apparently, part no 66120), the lucky line "key release" (part no 427), the EDCF keychain, etc. The little keyrings slide around the caddy in a "rail" of sorts; there is an opening at one point and a button on the back of the caddy that controls whether keyrings are allowed to slide to that position or not.