The Hohner CX-12 is available in F, E, Eb, D, C, B, Bb, A, G, LC (from high to low).
I.e. 5 keys above C, including D as the usual labeling is suggesting. Yours is apparently different. I shall find out, how Honner’s labeling is to understand, and what the others are like. (I have experienced with my XB-40’es that Hohner uses incoherent labeling sometimes.)
Seydel Saxony Steel and Deluxe Steel is available in solo LE, LF, G, A, Bb, C, D, and in orchestra C and irish G, A, C, D (irish means here, that pressing the slide is lowering the note by a half tone. All Seydel chromatics with steel reeds are available in various special tunings by the customer’s choice with the Seydel Configurator. The choice is only limited by the availability of the requested reeds.
Oh, I know what you mean. I have not yet done. But I have a 16-hole Larry Adler (Hohner 280) here lying around, in dismounted state, awaiting this operation since quite a time. Originally oldstyle nailed. The exchange of the nails against screws is the only thing I have finished up till now. It is not only 64 reeds to retune, but also replace 58 valves. At least those had been worn and need replacement anyway. But I have no use for 2 of it in C, and I like the sound of this fine old Instrument. I think it would fit very fine into Irish, Scottish etc, especially because of the additional low octave.
How do you come upon this? Afaik it is only necessary to rise all reeds by 1 wholetone (i.e. 2 halftones) constantly throughout the total range. Emphasis lying on "all reeds", and all by the same interval, as long as you do not want to change the blow-draw-pattern of the instrument.
(to be continued)