As promised - further info...........
OK, my initial thoughts on this (not posted) was I believe correct - it is the start valve to supply compressed air to the torpedo motor and auxiliary systems (i.e. gyro).
The "L" shape lever is a common feature, especially in earlier torpedoes where it protrudes externally from the torpedo body via a slot (inside the torpedo tube) and when the torpedo is fired by the external system, it levers & mechanically opens the value to the internal compressed air supply as the torpedo egresses from the torpedo tube - basically starting the torpedo motor.
The distance limiter mechanism forces the "L" back the other way shutting off the supply after approx. 4000m.
BTW - My google translation of Italian sucks!!!! (but then my English is no better )