Valley V4800 square escutcheon removal

[NWTennesseean]

How is the Valley V4800 square escutcheon removed? Does it unscrew, or is it pulled out? I presume (after removing handle) that the escutcheon must be removed first in order to expose the retaining nut that secures the cartridge. This is a 2-handled Valley shower, circa 1974. I need to replace the cartridge/seat/springs (untouched for, yes, 45 years) as it is leaking just a bit around the cartridge (no drip from showerhead, but replacing seat/springs in addition to cartridge for good measure), and don't want to break anything along the way. Incidentally, in case the retaining nut is a bit stuck, what is best to help it along? Vinegar? Penetrating oil? Thanks in advance. I've changed many a Delta/Eljer sink faucet, and this is very similar, but the escutcheon is an additional item on shower. I have a tub with round escutcheons that simply unscrew, but I don't want to assume anything.

 

[SHEPLMBR]

SET SCREW?

 

[NWTennesseean]

No set screw. I'll post a parts photo. It encircles the nut holding in the cartridge.

 

[NWTennesseean]

Helpful associate at plumbingsupply.com just told me it is an interference (friction) fit, with possible a bit of silicone behind it, so it evidently just pulls straight off.
My secondary concern is the retaining nut that holds the cartridge in place. If there is build-up of minerals from its 30-40 years of being in place, what is best way to help it loosen up to turn on its thread? White vinegar? Penetrating oil?

 

[Jeff Handy]

Use both.
Vinegar for several hours, or even overnight, you can mush paper towels soaked in vinegar over the spot, to keep it wet.
Then penetrating oil, for as long as possible.
Try gently tapping on the valve like with a wooden spoon, the vibration helps the oil start to creep in there.