One has to pause and define the meaning of export production.
As a general rule, the makers were small and produced for the Japanese sportsman. Of course, as they were mostly bespoke guns, they could have been built for foreign business men, diplomats or visitors. Then they would have been taken out of country.
It is my understanding that they were not mass produced for export from Japan.
There was and still some wonderful hunting in Japan. Much restricted now though.
I don't wish to leave an impression that millions were built. Certainly many thousands were, but many were destroyed during the war. Enough remained to cause problems for a new pacifist Gov't in dealing with a newly almost disarmed population.
Perhaps, with study and luck, we should know the answers to questions ie these guns. It does not seem possible that the forgings for actions came from England as no records have thus far indicate such.
There is one interesting detail about my Westley appearing gun. The receiver seems resistant to rust and it is not case colored. Perhaps the steel has more chrome in it than most.
This is interesting.
Best,
John