New (1974 vintage old stock) noise-cancelling microphone made by Telex primarily for aviation use in noisy environments. 

If you want to use this on stage or in the recording studio, you will have to find an adapter or change the PJ-068 plug to a standard 1/4" or 1/8" plug.

Noise Cancellation
The 66T microphone provides excellent noise cancellation and speech intelligibility in moderate noise environments. The microphone discriminates against all sounds more than 1/2″ away.

Microphone
The microphone is gain adjustable through an opening in the back of the microphone using a small, flat–blade screwdriver. The microphone is supplied with an adhesive label which may be placed over this opening after adjustment to prevent tampering.

The device consists of dynamic microphone cartridge, transistor amplifier, and push–to–talk switch in a rugged, black plastic case. A hanger bracket and mounting hardware are provided with the microphone. It comes in a 2-tone box measuring 7" x 5" x 2".