Hmm...maybe I answered my own question:
Guitars produced by MatsumokuNearly all guitars produced by Matsumoku (beginning sometime late 1976 or early 1977) bore serial numbers indicating the year and possibly production sequence. A small number of guitars produced had serials preceeded by a letter, but as to what the letter inidicated is yet a mystery and one can only guess without concrete evidence. I have seen both 6 and 7 digit serial numbers (excluding the letter if it is present).This new serialization covered Aria, Aria Pro II, Vantage, Westbury, most Westones, Japanese Washburns, some Electras, and the Skylark as well as others. As far as I know, the Korean version of these labels bear 8 or more digit serials and sometimes the production locaciton code (letter indicating Korea, Phillipines, Indonesia, etc.) which does not concern us here.
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The first digit (and upon rare occasion the first two) indicated the year. There is an inherent flaw with this single-digit method as the single digit year indicator will re-cycle after a decade! Attention must be paid to when the particular model was available and apply that to the first digit of the serial, excluding the letter if present. A bit of cross referencing is required. For example, my first Cardinal CS-350 has the serial 2010237 which indicates both by the first digit and the duration of the Cardinal CS-350 run it is a 1982 (and I know it is, I bought it then!). In rare instances the first two digits would indicate the year, in which case we can safely assume that my Cardinal is not a 1920! Had it been the two-digit version it would have begun with 82XXXXX rather than 20XXXXX, which would also indicate 1982.
.Spotting and identifying early Korean models after production shifted to Korea...Early Korean models adopted similar looking serial numbers but were not indicative of the year manufacturered. Many early Koreans appeared to be nearly identical to the Japanese models with one important thing missing, at least on models with bolt necks and neckplates: "Made In Japan" or "Product of Matsumoku". Without this, it is not an earlier Japanese model. Other tip-offs to later Korean heritage are bridges with squared-off ends, 3rd fret scarf joint in the neck, Schaller style tuners on models previously equipped with keystone style tuners, smaller potentiometers, and Quck-hook tailpieces with standard stop-bar stud spacing among others.