The General Electric 97U29 microphone was manufactured by Shure Brothers from around 1948 through 1968. It’s a sturdy, all metal mic and usually contains a Shure 99A86 element. I love buying this microphone. The design is wonderful, and is sometime repurposed for motorcycle tail lights.
From the 1956 Shure Brothers Catalog:
“510” Microphone Assembly
Controlled Reluctance Microphone and Desk Stand Assembly-ideal for fixed-station used in all types of communications work. Has a built-in switch for controlling both the microphone circuit and an external relay or control circuit. Replacement for Mfrs. Model No. CR84.
Model 510MD list Price: $42.50