Dear Befuddled of Bishop's Stortford,
(and all us other confused souls here), it would appear that the definition of these more unusual models might also have caused some dificulties for the staff at Wheatstone's:
A friend of mine has a Baritone that carries the serial number 29393 (just two instruments before the one in question here). It is also described as a Baritone Treble with the model number 20C, it being a 64key Aeola. It is a very long time since I had that instrument in my hands but from memory it is a standard Baritone with the buttons in the same places as a Treble but sounding an octave lower, as in Geoff Crabb's diagram above.
I am currently trying to get my friend to confirm the layout, however this use of the same model number for two very different Baritones made at the same time may explain why there was a change to identifing the Baritone-Trebles as numbers 14,15 and 16 during the following year.
In a previous thread where BT's were discussed , cannot find it at the moment, SteveS said that he has one which was made much earlier than the apparent 1923 starting date. This could suggest that there were many more produced than those that can be counted by these later designation numbers.
Edited by Geoff Wooff, 21 October 2014 - 01:06 AM.