The instrument
The D 19 launched in 1953 is the first with 200 ohms. It was also produced for Telefunken and Revox. Many variants were made, reflected in the letters after the model number. The D19C used a three‑pin locking DIN connector. The D19E used an XLR with a five‑pin connector, who presented all three options 60Ω, 200Ω and 50kΩ ‘Hi’.. There was also a D19B; it’s not clear what the B referred to, but some D19Bs were designated BK Hi. The K indicates that they had a captive cable and the Hi that they had a high‑impedance output for connecting to tape recorders. Some D19s with the suffix S had a large on/off switch. (soundonsound)
Details
"The frequency range of the D 19 should extend from 30 ... 16'000 Hz; its smooth frequency response must deviate no more than +- 3.5 db from the flat ideal curve. The distortion at 1000 Hz and 180° angle of incidence of sound should be better than 18 db. A continuous bass attenuator should cover a range from 0 to -10 db at 50Hz and be easily controlled by an adjusting ring located on the neck of the microphone." (Manual AKG D 19)