How to remove an Ann Sacks shower cartridge?

Does anyone know how to remove the cartridge from an Ann Sacks One thermostat shower? I removed all the trims but then there is a thick metal ring covers the cartridge. The ring can be turned but it doesn't screw out.

This is what the valve looks like after all the trims are removed.

http://lh6.ggpht.com/_kw6AN1uqJhc/TO8SOrhsSAI/AAAAAAAAFyI/HS-9ToM0O5U/s800/IMG_4776.JPG

Normally you would unscrew the piece that has the "EF 009" sticker on it. But that will not help a whole lot unless you have a replacement cartridge, and if you do, the process should be apparent from observing it.