Essentially none of any importance. Each country was overwhelmingly supplied by it's national arms industry (and some were assisted by American Lend Lease.) Additionally worldwide naval dominance of the Allies (except in the Japanese sphere) meant that few countries had a choice of which side they traded with. The few smaller countries that maintained neutrality typically needed what homegrown arms industry they possessed to supply their own forces.

A few pre-war gun designs from firms like Oerlikan in Switzerland and Bofors in Sweden were used and produced by both sides, but the actual manufacturing was done in German, British, American and Japanese industrial plants.