MCM Perpetual Rotating Calendar 🐞

MCM perpetual rotating calendar. Stamped/marked to the back with “D.R.G.M.” I don’t know the significance of these letters. The days of the week can be changed by turning the two knobs on the side and the knob on the back. The month labels are all present and in good condition. There is a written date of 1942 on the inside. Good condition considering the age. No issues. Any wear commensurates with the age. I do believe the body of this piece is composed of metal. Approximately 3.5” wide and 6.5” in length.