Old brass shower handle plate not coming off

[bigworm]

This is a pretty old brass two handle shower, the cold water handle is leaking water. I got the handle off but could not get the plate off. It is round and it does not have screws or anything to hold on. What is the brand and how to get it off? Thanks

 

[Geofd]

maybe it threads off

 

[bigworm]

not moving at all, actually I do not find a good away to screw it off, because it is round.

 

[Geofd]

not moving at all, actually I do not find a good away to screw it off, because it is round.

is it possible to get a strap wrench on it or try a couple of thin small flat head screw drivers and gently try to pry
it off

 

[Jeff Handy]

Might be caulked on from behind?

 

[Jeff Handy]

Since it looks like $#it anyway, I would try to grab the outer rim with a big pair of channel locks, and rotate counter clockwise.