If I remember the model correctly, it was meant to be a sort of 'live' 414, cardioid only, for drums, cabinets, overhead, etc, built into a robust body. I believe it is a true condenser, and the diaphragm is based on the 414.
Documentation (including service docs) can be found at http://www.akg-acoustics.com/site/products/powerslave,id,814,pid,814,nodeid,2,_language,EN.html
JC