It looks kind of like this:
Except it doesn't have those two bolts that are shown partly backed out in the picture. Instead, it is a solid piece like the other half in the picture.
So the only way to disassemble it seems to be to remove the circlips on one of them and drive the "cross" out.
Does that seem right? And if so, does it matter which of the four sides I drive out?
Do I just drive it out with something that fits in there (I'm thinking a socket), and then just drive it back in the other way to reassemble?