This thread started by
http://www.subsim.com/radioroom/showthread.php?t=186112
Led me to accidentally come across what may be the most important document in SH history, at least where torpedoes are concerned. It contains the complete story of the German Torpedo Crisis, including the exact date of the order to stop using the magnetic pistols, the date of the order to start using the new ones and the fact that starting in 1943 they did indeed have a switch that would enable both impace and magnetic pistols or impact only!
http://eaglescholar.georgiasouthern...._201005_MA.pdf