In the Army we only used to see the little one on the right. Forget the official designation but Beery is probably right, it was the No2 Mk4 and we also had a big Webley 1.5" signal piustol with lugs around the barrel and a locking catch. Over complicated for what a signal pistol really needs to be BUT, on the plus side. it used Webley .455" Mk6 grips which was handy if you happened to have a Webley Mk6 - which I did at the time.

The little No2 'tin-plate' signal pistol was always known to all and sundry as 'the Berridge' signal pistol. I didn't know it then, but it was so called after the pressed steel company that made zillions of them. The peoblem with them was that the BA screw threads on the side plates would strip if you put more than about .001foot/pound of torque on the screws. You COULD ring punch them but......... anyway! Someone will correct me if I'm wrong but I seem to remember that some of the trigger mechanism parts such as the hammer and mainsprings etc etc were interchangeable with the little 2" mortar which we called 'section artillery'

Also notorious for missing serial numbers. I mean even more notorious than Fazakerley Stens, Sterling SMG's and No4's. So you'll often find these with the lost number type engraved into the left hand side frame such as SA80A xxxx