exert taken from neumann forum:
Since there were three types of capsule (KK 83 omni, KK 84 standard cardioid and KK 85 speech cardioid), all of which could be used interchangeably on the same amplifier type, in practice it became fairly common for amplifiers to have capsules on them which were different from the model which would be implied by the amplifier's own markings. For example a microphone whose amplifier (body) was marked "KM 83" could very well have a cardioid capsule put on it, such that it would really be a KM 84 until/unless someone were to put a KK 83 capsule back onto it.
For this reason, in the later years of production, Neumann stopped inscribing "KM 84" etc. on the bodies, and instead wrote just "KM" or "KMi". You always have to look at the capsule in order to know exactly which microphone you have."