Nathan AirChime's M
Series horns were the first major production locomotive chime
horn to be produced. They are constructed of sand cast bells,
heads and manifolds, and have multi-piece bronze diaphragms.
M horns have a classic, mellow sound that is unlike other locomotive
horns. The M Series horns require re-tuning about every
six months when in regular service. Any bell of and M horn
may be reversed ("R" in the name of the horn denotes
the following bells being reversed). The most popular models
are the M3 and M5. Although the market share of M Series
horns has dwindled, they are still offered today.