Strack provides accurate dates, but I have seen the Japanese on the ground there for years, and have been telling people long before Strack came out in English. They buy everything in some sizes, and good luster and better in other sizes. You see the same factories at the shows selling differentiated Chinese and Japanese, but strangely the high quality Chinese is never there, and neither is the low quality Japanese. So what happened to the top grade Chinese? How is it that although the large part of every harvest in Japan is of low to unacceptable jewelry grade, yet you never see it? You do! It is marked as Chinese.
It does not take a genius to see what they are doing. That is why I feel so strongly that sellers of "Japanese Akoya only" are unethical, or in the least, uneducated.