While best known for inventing the electronic musical instrument the theremin, Léon Theremin also designed one of the first bugging devices to passively transmit audio signals. A forerunner to RFID (radio-frequency identification) chips used in inventory control and as anti-shoplifting technology, the so called Thing (the first of its kind) or the Endovibrator (Эндовибра́тор) was embedded in a carved wooden seal presented to the ambassador of the US diplomatic mission to the Soviet Union by the Young Pioneer organisation (see also) as a gesture of friendship on this day in 1945, shortly before the end of World War II. Ingeniously, a small length of antenna requiring no external power source would vibrate, picking up voices in the embassy office and could be demodulated—without risk of detection by a receiver tuned to the right station.