U.S. Military binocular mounted Polaroid filter, MI

Metal frame lens filter assembly has two variable darkness mounted Polarizing filters with dual side control to set level of light entry into the binocular. These were issued to military personal who required minimal light reflection of bright surfaces such as Navy personal and ground spotters for reflective sky viewing. The filters work as designed with the filters offering a green, light to dark tinted view, see images. The M1 designation imply's these were the first issued,