Wiljan:

According to the Time-Life Books, 'The Seafarers" series,
'THE U-BOATS", page 23: "The trigger mechanism included an ingenious safeguard against the terrifying possibility of an inadvertent
detonation: It was capped by a safety lock in the form of a tiny propellor that spun itself off a threaded shaft and fell away after the torpedo had run about 30 yards on its course."

This book was published in 1979. A submate of mine just loaned it to me today, after I asked him the same question. He said that when the little brass arming propellor fell away, the contact and magnetic-influence features of this pistol became fully armed.

Best regards,

ROBERT M.