SPECIALLY MODIFIED VIBROPLEX KEYS WWII BY RUSSIA.Made in the USSR at the beginning of the Great Patriotic War for use communication lines of special radio services. A limited number of such telegraph keys during war produced the "Электроприбор” [Electrical Appliance] Moscow plant. These keys were specifically designed to eliminate identification of unit Morse operators by Gestapo intercept operators who used such signal intelligence to know the locations of Russian military units and attack them.73DR