The latest fashion in horn mouthpieces is to have a gold plated rim. I'm sticking to my favourite nickel silver Paxman 4B. I have two, one I got with my Christmas money when I was 13 and the end that goes into the horn has worn nearly square, which probably explains why it doesn't fit into my Alex (103). That and the fact that the tapers are different.
And you thought it was just organists who were all anoraky about such things.