Someone pointed out me in private, rightly I would say, that I stated that these fuzes are made in Italy, but without any evidence and I apologize.
So let me explain why these switches are surely of Italian production.
All Italian fuzes derived from English "number switches" are easily recognized by the presence of this bushing.
which is used to hold the percussion detonator model OTO.
The Italian version of the Switch No. 4, called ST-1 (ST-1 = Strappo 1 = Tripwire Type 1), is recognizable from the body made in a light alloy called zamac.
Even fuze RP-2 (Rilascio di Pressione 2 = Pressure Release Type 2), version of Switch No. 6, has the zamac body.
Moreover the pivot of the lid passes through a characteristic "hump" formed on the body of the igniter.
I hope to have cleared all doubts.
Regards
stecol
P.S.: For these info's there are no websites, only field or technical manuals ...:tinysmile_twink_t2: