Smoking pipe sends radio transitions to CIA operatives!

OK, now this is just cool.  This pipe is from an online collection on the CIA's website.  It's a sub-miniature radio receiver that is concealed in a modified pipe.  The user hears the sound via "bone conduction" from the jaw to the ear canal.  How cool is that?

Here's the link to this pipe, and be sure to click around the entire collection.  https://www.cia.gov/about-cia/cia-museum/experience-the-collection/index.html#!/artifact/131