Yeah, since mouthpieces don't actually get paid for doing anything and since they also don't give performances, don't give lessons, don't pay taxes, etc., it would be a mistake to call one "professional".
If the question is whether a mouthpiece is USED by some professional(s), that's a different question -- and I'm pretty sure that at least SOME professional musicians (who perform, give lessons, and pay taxes) use this mouthpiece.
You seem to be feeling some guilt for abandoning your old mouthpiece which stood behind you, was faithful to you, and was good for you for many years. And now you've taken up with some "professional" English floozy. Life is full of difficult choices, and some error. I hope you can work through this moral quandary and do the right thing. Otherwise your practices and performances may be affected severely.
Gary Merrill
Wessex EEb Bass tuba (DW 3XL or 2XL)
Mack Brass Compensating Euph (DE N106, Euph J, J9 euph)
Amati Oval Euph (DE 104, Euph J, J6 euph)
1924 Buescher 3-valve Eb tuba (with std US receiver), Kelly 25
Schiller American Heritage 7B clone bass trombone (DE LB K/K10/112/14 Lexan, Brass Ark MV50R)
1947 Olds "Standard" trombone (Olds #3)