I'm having a bit of a problem getting the valve stem out to replace, with a 2 handle system. I can get the knob off, and the chrome cover comes off just fine. However, there's another sleeve that's made of copper that surrounds the stem, with only a few millimeters distance between the two. There doesn't appear to be any nuts or anything to use a wrench or socket on. I also cannot unscrew the valve stem, as it looks like it's just screwed into the piping in the wall. It's pretty corroded, i've sprayed with WD40 and gotten nowhere. Anybody have any ideas? Also, not sure on the brand, I don't see that info anywhere. This house was built in the early 1920's and it's looking like things were updated in the 50's?? I've attached a pic that may help with figuring this out.