This is a Bach trumpet mouthpiece, model 5SV. It's a model supervised by Claude Gordon. It has been modified with a rim change, and the rim is reportedly cut from an Artisan model 7E. The original rim was already quite thin, but I suspect the goal was to make it feel a bit smaller than the original. The rim threading appears to be Bach standard, but depending on the mouthpiece, it sometimes fit and sometimes didn't. Please note this. I believe there are no other modifications besides the rim change.