No such thing as an M-200, there is however an A-200. That is what many late era steam locomotives had.

Alf Doten Wrote:
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> The single chime air horn in the front was a
> Nathan M-200 or something close to that like on
> the AC's and GS's. Maybe someone can "chime in"
> otherwise. The steam whistle sounded like 2472 as
> a reference, but I remember hearing some god-awful
> out of tune or damaged whistles at the end of
> steam heading up the Altamont through Pleasanton
> and Livermore. Often the air horn was
> plugged up and just as bad.