The Bofors 40mm born in Sweden in the '30s and became, probably, the best anti-aircraft gun of World War II.
Bofors was great at selling licenses - the Americans shelled out $500,000 in 1941 (serious money back then!), the British bought the license in '37, and basically half of Europe lined up to get it.
But the Germans... played it sneaky! Instead of paying, they waited to conquer half of Europe and just took all the Bofors guns they found lying around, renaming them "4cm FlaK 28". Classic German style: "License? What license, we'll take them for free!"
Americans were mass production maniacs - they took the Swedish design and completely overhauled it to pump out 39,200 of them! The British instead made a mess of different versions (Mark I, II, III... all the way to XI). The Japanese copied the ones captured at Singapore.
With all these countries producing 40mm ammunition - Americans, British, Germans, Swedes, Canadians, Australians - the projectile in the photo could be from anyone! They were all compatible but each had their own little details.
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