Yeah, that's what I seem to recall reading recentely.
http://www.josephson.com/tn5.htmlC. The Jecklin disc in practice
II. Operating instructions
1. General
The disc has two microphone mounts (21mm) and one stand connecting piece. By putting the stand connecting piece into the individual borings, the setting angle of the disc can be adjusted to any situation. The measuring cord located in the center of the disc serves for the adjustment of the microphones on the disc. The measuring cord can be adjusted on both sides.
2. Mounting of the microphones onto the Jecklin disc
The microphones are pushed from the rear through the holding clamps of the "Jecklin disc". Take care that the microphone capsules on both sides are located at a distance of approx 8 cm directly above the disc center. This can be checked by means of the pulled-in measuring cord. In this case, the angles of the microphones are drawn slightly towards the outside.