The M3 was the standard U.S. Army binocular of WWII. It was made by Nash-Kelvinator and Westinghouse; and B & L, Universal Camera and Wollensak are also mentioned as manufacturers. B&L and other optical giants made most of the optics for the various manufacturers. There were minor differences in weatherproofing, reticles, and possibly some were coated. The M3 incorporated an improvement, a set screw to hold the eccentric ring objective cell, to keep it from rotating during heavy use. The M3 has a 8 degree, 30 min. FOV, an f 4.4 objective, and the reticle is graduated in mils (horizontal) and hundreds of yards (vertical). 311,263 were made, at a price of $71. Production stopped in 1944.
The marking H.M.R. is maybe the initials of an inspection team responsible for the ordnance material accepted by the Army from a factory and/or region, or it could mean "High Moisture Resistance"