Shower Cartridge Help

[Mkrahn70]

I took the handle off and tried a bit to unscrew the collar, did not budge. Do I just hammer away until it loosens and I can unscrew it or can I possibly do damage? Small leak so planning to replace the cartridge (and new handle) if I can get to it. Thanks in advance.

 

[breplum]

Severe and terminal damage can occur if you just put channel locks on and try to unscrew the cap because of the way it is made.
look up Delta old style cap removal on youtube and see if you can learn some techniques. you will need to remove the plate. and don't bother with penetrating oil...doesn't work, ever.

 

[Twowaxhack]

Looks like a Valley faucet.