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.