First appearing in 1959, the AKG C24 is essentially a stereo version of the legendary C12. In 1976, Sheffield Lab and their founder Doug Sax, (of Mastering Lab fame), made a retro-revolutionary recording of Harry James and his Big Band, using a single AKG C24 stereo tube microphone. The resulting audiophile LP, "The King James Version", was a throwback to the days when a performer had to cut their music ‘live’, directly to a wax cylinder. It was only one of many releases by Sheffield Lab, but it was one of the most unusual.

Setting up the band in a chapel down the road from the lab, the Sheffield team recorded the big band ‘direct to disc’. The signal went from the AKG C-24 stereo mic, through a small mixer, then straight through 600 feet of cable to a cutting lathe in the lab, to make a vinyl pressing master. Nothing else got in the way of the signal path. The results were nothing less than amazing.

Using such a large ensemble to make a truly live record was a daring experiment, a testimony to the faith that Sheffield had in the performers. Using the AKG C-24 stereo microphone to capture the sound was not daring at all, but it was a testament to the faith that Sheffield had in the abilities of this legendary microphone.

From the original brochure:

"The C-24 was specially designed for intensity stereo recording techniques in the XY or MS mode. Two twin-diaphragm condenser microphone capsules are mounted within the microphone body, with a spacing of only 1 1/2", making any difference in time between the two outputs negligible. The upper microphone system may be rotated 180 degrees to provide any offset angle desired. Nine different directional patterns can be remotely selected for each of the two twin-diaphragm capsules. These patterns are identical as to their phase relationship and sensitivity and maintain their polar characteristics independent of frequency. The patterns are a) omni directional, b) cardioid and c) figure-eight, plus 6 intermediary positions.

The stand connector is designed to facilitate rapid and accurate change-over from MS to XY stereo recording technique. A window indicates the symbol MS and upon rotating the stand connector by 45° counter·clockwise the symbol XY indicates the correct XV position.

The C-24 system consists of microphone preamplifier with two twin-diaphragm capsules, S-24 dual remote control pattern selector, N-24 a.c. power surply, MK-24/20 cable for connecting microphone and power supply, RL-24/10 cable to connect power supply with pattern selector.
I have owned this mic since the Early 70's.  It has been carefully handled and used.