since it's already the 25th here.
For Daini vs. Suwa start dates, I think the answer is found in "A Journey in Time" - i've got a PDF copy & am scanning thru it now
OK - finding the info seems like it's going to take a while, I'll just put in this placeholder for now & edit it later if I find the answer.
UPDATE: OK, there was a Seikosha clock & watch plant for many years under "K. Hattori" (original name of what we now know as "Seiko").
"Daini" refers to "second" [2nd] in Japanese, and a new company & factory was set up in 1937 as "Daini Seikosha Co., Ltd." [much later as Seiko Instruments] which took over the watch production activities of the Seikosha plant. Daini Seikosha company had at least 2 plants, Kameido [which was destroyed in the March 9, 1945 bombing raid on Tokyo] and Suwa [located in Nagano Prefecture]. I see reference to "Daiwa Kogyo" & "Daiwa Kogyo Ltd." as a factory/subsidiary having been started pre-war in the Suwa area & to which many machine tools, etc. had been transferred (from the Tokyo area) thus saving them from wartime destruction & allowing "Seiko" to resume production by about Aug 1946.
Post War, the Super was designed & produced out of the Daini Seikosha Suwa plant starting 1948. The Kameido facility then "responded" with Unique... So, this was the start of the "rivalry" or corporate competition we see going thru the '60s & '70s [and highlighted by this discussion of LM vs. LM Special vs. LM DE LUXE]. At that time though, it was between the "Kameido" factory and the "Suwa" factory, both under Daini Seikosha company. "A Journey in Time" goes on to highlight the competition in the context of the Swiss Observatory Chronometer competitions/trials in the '60s at locations Neuchatel & Geneva.
Note that the watch insignias used during '60s/70s tie the "divisions" to those old factories. The "Kameido" (thunder) logo was used by "Daini division" [looks like a lightning bolt w/ 3 lines] while "Suwa division" used a similar logo, but with a "box" design in the center. So, the "Kameido" factory came to be the Daini Division, while the Suwa plant became the Suwa Division (roughly speaking). A time-line in "A Journey in Time" shows the "Suwa Seikosha Co., Ltd." being formed appx. 1959 [later becoming Seiko Epson Corp.] out of the merged Daini Seikosha Suwa plant and "Daiwa Kogyo Ltd."
Now for "why do we see more Suwa watches?" - or at least seem to see more Suwa. In my notes is a statement that "Daini made most of the ladies watches... Suwa made most of the mens watches" referring to 1960s. Since most collectors seem to be men, and mainly concentrating on mens' watches, this would explain some of the apparent predominance of Suwa products. I think also that many of the Suwa products of '60s & '70s may have been more geared to (Western & Australian) export markets, while most Daini products were more domestic market (and nearby Asian market) oriented. Since many collectors on the forums are NOT based in Japan, they probably see for sale many more "export models" than JDM models offered for sale & discussed. I don't have hard statistics on that last conjecture, but from the English language catalogs I've seen, I think most of the men's watches I've seen offered were Suwa products.
Here in the Philippines, on Philippine eBay, in the past year, I do think though that when it comes to late '60s/70s Grand Seiko & King Seiko products, that Suwa & Daini products are about equally represented - of course, none show up in great numbers so the "sample size" for statistical purposes is relatively small & thus more prone to "error" for making conclusions out of that data.
Also note that it was Suwa that 1st created the Grand Seiko line in 1960 [calibre 3180], I believe Daini's 1st GS was the 4420A, but not till 1964. In addition, it was Suwa that produced the 56 family of automatic-wind Grand Seikos, which transitioned from "hand made" to mainly "automated" production methods, lowering the beat rate of the Suwa 61GS automatic movements [36,000 bph] to 28,800bph for that purpose. Daini did not seem to produce a competitor to that 56GS family, just sticking with the hand-wind 36,000bph 45GS family until mechanical GS production was phased-out during the "quartz revolution" of the '70s. So, Suwa's automated-production 56GS probably was produced in larger numbers than contemporary, competing Daini GS products.
From what I've seen of older Seiko advertising, this distinction of Suwa vs. Daini was NOT made known to the buying public, so it's more of an issue of arcane "Corporate Culture and History" that us "watch geeks" [and probably MBA students doing case studies] care about.
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