Need help with shower stem valve removal

[Tfua]

Trying to remove leaking shower valve and having hard time. It has a 5//8 hex nut then these concentric circles behind. Tried turning hex, won't budge. Also, If anyone could identify this valve that would be wonderful. Thanks!













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[Mr_David]

Make sure the valve is open before you try to unscrew it.
put the socket on the hex and get a bigger wrench. the longer the handle the more you can put to it.. Don't bust a knuckle or?