Posting for a friend...
He has an older Conn with the nailfile G# key - I think that in reality it is called a 'New Wonder Series II' but most people use the nickname of 'Chu' for this model. I suppose it is probably a 1920's Conn...
I had a similar Alto years ago, gold plated, but I never really liked it. I used it as trade bait for a 1931 SSS cigar cutter and never looked back.
I can't ever remember playing a Tenor of this same model.
Anyway... my friend is looking for a mouthpiece recommendation for something that is a bit 'bright' that would play well on this old Conn. Unfortunately, I didn't think to ask him what he is currently using for a mouthpiece. Since I have no experience playing on one of these I told him that I would post and see if anyone here on SOTW could provide some mouthpiece recommendations based on their own playing experiences.
I am going to loan him a Moragn 7EL to try as an experiment. I'll have to mail it since he and I do not live near one another so it will be a couple of days before he can try out the Morgan and report back.
Since stumbling onto a Morgan (Alto - 6E) about 15 years ago I have played them pretty much exclusively since then.
I have a feeling that a Morgan 'EL' will work well on this model of Conn.
How about a Berg ? Does anyone out there play a Berg on a Chu with good results ?