Steve - your information about the use of pistols in the Japanese Police is not correct. I just finished working an hour on a detailed reply to your remark, and it disappeared from the computer, a problem that goes on and on. I simply cannot take the time to redo it.
If you can find a copy, I wrote an article on Post-war Japanese ammunition with the help of the former Director of the Japanese National Crime Lab, Hiromatsu Ikeda San, and vetted again in 2000 by that agency’s Tsuneo Uchiyama San (who found two minor errors and added a small amount of information), that appear in the Bulletin of the California Cartridge Collector’s Association, Volume 17, Numbers 4 and 5, issues of August and October 1997. It would go some way to answering your question.
Remember, it only goes to 1997, and also remember that there are many different police Agencies in Japan, just as there are in the United States.
I am sorry my first answer was lost, but all I can say is c’est la guerre.