I have in my collection two signal pistols. From the research that I have done so far: the one on the left is a Pistol, Signal No.2 Mk.5 and the one on the right is a Pistol, Signal No.1 Mk.5.

The No.2 Mk.5 obviously has a shorter barrel and no extractor. It also has a small round stud on the let side. Various people on the www have stated that this is for attaching the pistol, to a port in an aircraft or an armoured vehicle. This strikes me as being nonsense because, having fired No.1 Mk.5s umpteen times in Britishicon service, I am sure that that small stud would be ripped off by the recoil in no time flat. (Take a look at the very much more substantial pair of lugs on a No.4 Mk.1 .15inch pistol.)

I'm coming to the conclusion that the stud may be for locating a a barrel extension.

Any comments are welcome.
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