Going up and down the web I found this link:
http://www.cockpitinstrumente.de/arc...nenkanone.html
were MG (MK) 101 gun is technically explained with german text, photos and more.
Please scroll down the page and have a look at the PDF and .doc documents. One of the most interesting (if authentic) is the Messerschmitt one dated 22.2.1940 where the gun is coded as MK 101!
All the best.
Ric.