Re: Something to "Chu" on..............
The first change that you see coming out of the Chu model is that the engraving went from a floral to an art deco style. Then you begin to see real changes in the physical character of the horn as detailed below, then you see the engraving change again from the art deco to the lady in a pentagram, then you see the 6M or 10M stamp, and finally, removal of the forked Eb key.
Keeping in mind that Conn was very experimental in the late 20's through the30's and exceptions do exist (for example, I have a Conn bari sax with same side bell keys like a 12M that is serial number 223xxx), I'll post my observations as they relate generally to serial numbers and the transition from the Chu to the 6M or 10M.
SN 235892 - the last floral engraving I've seen on a Chu alto.
SN 238976 - the first art deco engraving that I've seen on a late Chu alto
SN 244377 - the last split bell key Chu alto (up until this point the altos have been late Chu Berry's with the exception of the engraving, so they were not true transitional in any mechanistic sense)
SN 245372 - the first Chu alto with same side bell keys (now these horns feature Chu Berry style table keys, forked Eb key, same side bell keys, under slung double socket tuner neck, raised top side key (high F), adjustable thumb rest)
**Note because these horns feature both mechanisms of the Chu Berry and the 6M, these are the horns we consider to be a true transitional model.**
SN 249976 - the last art deco engraving (These are also the last to sport the Chu style table keys. Some people consider only a horn with Chu style table keys and same side bell keys to be a real transitional model.)
SN 250404 - the first lady in a pentagram engraving I've seen (These horns now feature the more modern 6M style table keys but are not stamped 6M. There is debate wether these horns should be considered transitional. The only thing that separates them from a slightly later rolled tone hole 6M is the adjustable thumb rest and the 6M stamp.)
SN 275382 - The latest 6M with no 6M stamp that I've seen (also still has the adjustable thumb rest)
SN 278969 - The first 6M stamp I've seen (this horn also no longer features an adjustable thumb rest .
SN 235267 - last of the floral engraved Chu tenors
SN 236368 - first art deco engraved tenor (like the first art deco altos, these tenors are otherwise entirely Chu like with mushroom neck octave pip, split bell keys, Chu table keys, forked Eb)
SN 250872 - The first naked lady engraved tenor (again this seems to follow exatly in line with the altos. However, whereas the altos moved to same side bell keys and 6M style table keys, the bell keys on the tenors remain split and the table keys remain Chu Berry like for a while longer. Although, the tenors did changed the neck pip at this point. From this point on, the 10M neck will be featured with a funnel style octave pip. Most people consider these the first transitional tenors.)
SN 261436 - the last of the split bell key tenor and the last of the Chu Berry style table keys
SN 263072 - the first of the same side bell key tenors. (These horns also feature the 10M style table keys. However, they are not yet stamped 10M. Because the only difference now is the 10M stamp, most people do not consider these to be transitional tenors anymore)
SN 274794 - The first 10M stamp appears
SN 312547 - The last 10M to still have the forked Eb key
SN 316415 - The first 10M to be without the forked Eb (for some reason Conn kept the forked Eb key on the tenors for a much longer time than on the altos)