OM stands for Orchestra Model which was originally designed by the C.F. Martin & Company in 1930.
This modern spinoff is based on the same OM body dimensions and shape but with a some custom order requests. 
Ziricote back and sides with matching headstock overlays and sinker Red Cedar top. Grit Laskin Rib-Rest and top Bevel, side sound port, and Alessi custom tuners.