Thanks you for that . I never found anything written about these, nor knew the production totals. I have the one shown in Whitney that was taken at Tokyo Bay and I just serviced one that was completely unused (could not have been given some of the endshakes). He bought it a gun show for very little money (just last year). Incredible. Probably survived as a reference piece BECAUSE it was never correctly finished.
Both the Seiko and the Hamilton were patterned after the M21 and I have a pretty good understanding on the M21 from conversations/correspondence with Ben Hummel. The Seiko is a bit more mysterious.
Years ago I decided to see how close the Nardin and Seiko actually were. I was able to interchange all parts with no issues. The only difference is the finish. It is interesting to see they did the research to develop alloys for the Guillaume balance
I had pressumed the JIN brought the production on Island to hide their fleet build up in violation of the Washington Naval Treaty. Now I know that in fact they started production long after their capital ship production was started. Interesting.
And the the govt ran into the same opposition about getting a private operation into the business. Hamilton's arguments were almost identical.