I just bought a vintage grundig GCM3 microphone dating from around 1956 and I was wondering if anyone knows anything about it. I'm hoping it's a crystal mic, but I'm just not sure.
This is a very common microphone, but what sets it apart is the fact that this is a condensor microphone - not very common for a microphone for the consumer market. The english type is GCM 3, the german name is GKM 17. The model GKM 7 is similar (but rarer), it has a round foot and the grundig emblem in the middle of the grid.
Being a condensor microphone, it required a 100 V polarisation (supplied by some model Grundig tape recorders). From what I have heard, these microphones did a good job, much better than the average crystal mic or even dynamic mic from the same era !