nick hull wrote:
It would help to know the NAME of the valve. A bit of wiggling and
penetrating oil might help if there is no pin or setscrew holding it

yes, I agree and would have provided it it available

assuming any wild limited number of names (ie. harry, tom, sam, moen) - is there some
generic list of

1. if it is a "harry", then do ...
2. if it is a "moen", then do...

my guess is there is some kind of spring or clip inside a cover, right behind the
metal disc part (the part that one turns to make the shower come on) which I am unable
to access since removing the center screw will not take off the metal disc part

I could of course just take a metal saw and cut it off from wall but wanted to avoid
that if possible