Faucet Identification Assistance

I have a very leaky shower faucet I need to repair but it doesn't easily match up to the various descriptions I've seen online.
Old house (1917), old bathroom (4" tiles), dual handled (hot/cold) faucets for the bath spigot. Pretty sure it's a compression type but the stem assembly is throwing me off. Removed the handle no problem; there's a bell-shaped cover that snugs up against the tile which I discovered spins off - it's threaded into a brass nut in the shower wall.

So now - there's no easy way to remove the stem and access the washer I figure needs replacing (and probably seat repair) and I'm left to guess that the nut needs to be unscrewed out of the wall to release the whole stem assembly.

Before I do that, though, I'd like to get feedback from anyone that recognizes this faucet description and any other advice they might be able to provide.


There are special sockets made for this purpose. They are deep and have a large open end that the stem can stick through. The outside of the socket is square or octagon and it is turned with a wrench once in place.
Should be able to get this type of socket at a place like HD. They aren't expensive because they are normally cheap metal rather than a cast metal.