In 1945, Soviet schoolchildren presented the American ambassador with a wooden panel made of precious wood depicting the US coat of arms.
Neither the schoolchildren nor the ambassador knew that a listening device was installed in the panel, the design of which was developed by Lev Theremin. The "wire" was hidden so well that the American intelligence services did not notice anything, and the Soviet intelligence services listened to conversations in the ambassador’s office for another 8 years.
After its discovery, the device was presented to the UN as evidence of Soviet intelligence activities, but the principle of its operation remained unclear for several years.
The operation was called "Chrysostom" (or "Confession").