Thank you wschruba. Your experience is valuable. Which is why this forum is so good. I think I will take your advice and leave it on. When I use it, I will have to plan on a chainring that will work with the 20t rear sprocket. I did see threaded sprockets available on ebay. But if I can't get this off, why bother.

I am guessing that the sprocket is right hand, or normally threaded? I may try again later when I have a wheel built around it, but I will be planning on using it "as is" with the existing, stuck on sprocket.

I wonder if there is any advantage to the brass brake pads over the modern steel pads that we see on Bendix RB and newer and Shimano coaster brakes?