Very interesting site. https://www.cryptomuseum.com/covert/mic/mm61/index.htm https://www.cryptomuseum.com/covert/mic/mm61/index.htm > Although the MM-61 was

Very interesting site. https://www.cryptomuseum.com/covert/mic/mm61/index.htm https://www.cryptomuseum.com/covert/mic/mm61/index.htm > Although the MM-61 was originally intended for use in combination with dictation machines and the first generation of (large) hearing aids, it soon became a prime candidate for covert listening devices and recorders. When carried casually in the outer pocket of a coat, the microphone could barely be distinguised from a real fountain pen and would not raise any suspicion. Because it was overtly carried, the sound quality was superior compared to that of a concealed microphone Also, the woodworm: https://www.cryptomuseum.com/covert/bugs/holzwurm/index.htm https://www.cryptomuseum.com/covert/bugs/holzwurm/index.htm