moen cartridge

I have a Moen shower handle (unknown model) that doesn't seem to have a set screw. Before I go yanking on the handle, any thoughts on how to take this piece off?

Ok, I am in need of a little help. I watched a few videos and read a couple of instruction guides on how to replace a Moen 1225 cartridge. The replacement went well, and with the initial test it works fine. The problem happens when i get everything back together. When the water is then turned on...