Theremin 's device was embedded in a carved wooden plaque of the Great Seal of the United States . On August 4 , 1945 , Soviet school children presented the bugged carving to U.S. Ambassador Averell Harriman , as a `` gesture of friendship '' to the USSR 's World War II ally . Disguised in a replica of the Great Seal of the United States carved in wood , in 1945 Soviet school children presented the concealed bug to U.S. Ambassador as a `` gesture of friendship '' to the USSR 's World War II ally .