TromboneChat

I have a Conn USA 6H, serial 724757, purchased new approximately August 1957. I also purchased at the same time a Bach 11C mouthpiece which we discovered later, because I couldn’t properly tune the instrument, was for a smaller bore instrument. The dealer apparently did not have the correct bore mouthpiece so a machine shop built up the shank with brass and turned it to the proper size. It has served me well all these years. I have not been able to find anything definitive regarding the design bore size of this instrument. I did find a chart online stating it is a #3 bore, but it gives no measurement in inches. Can anyone direct me to information regarding the bore size? I am also curious as to when the instrument was built. Serial number charts I find online point to 1958, but I was playing it by 09/1957. I have been told that these charts are merely estimates, mainly due to companies changing ownership over the years. The music store where the instrument was purchased is still in business, operated by a grandson, but does not have records that far back. I would appreciate any help toward answering these questions.

Welcome

First, a 6H is 0.500" bore (that's Conn #3). It should take a small shank mouthpiece and an 11C should fit fine with no modification. The instrument came originally with a Conn 3 mouthpiece, which is a similar size.

Second, most serial number lists are approximate and yours being 1 year off is pretty good. Unfortunately, the records of the Conn Instrument Company from that period were destroyed by a fire so more detailed information about manufacture will be difficult to find.

There is a site called Conn Loyalist (https://cderksen.home.xs4all.nl/) that has lots of information on Conn musical instruments.

Thanks for the info. I thought the bore might be a little over 0.5 inch, since the mouthpiece shank had to be built up. But that was a few years ago. Memories fade.