RCA 77D Ribbon Velocity--- 1945-58
The 77D is high fidelity Polydirectional microphone. This mic is
similar to the 77DX but was made 5 years earlier. Instead of being
open on both sides as in the conventional velocity mic, this mic is
coupled to an acoustic labyrinth which forms the body part of the
Nat D. Williams was the first black DJ on WDIA in Memphis