[Geoff Winnington-Ball (RIP)]

The one you pictured is Canadian in design and manufacture; we made a sum total of 24 of them early in the war, primarily for west-coast defence against an imagined Japanese invasion. There is a surprisingly large percentage of them still around, but that's because they were never shipped overseas (except for the odd sample given to the Brits I believe).

The one(s) Keefy has shown are of Australian design and manufacture, and are unique.