History Initial construction was in Japan by various manufacturers/factories from 1970 through 1983.The first Sigmas were typically dreadnought acoustics, although Grand Concert Series (GCS) and classical models were also produced from the early 1970s (1971) onward.All other text was printed in black ink, or stamped on in ink by the manufacturer (model and serial numbers.)From 1980 through 1983, the end of Japanese production, the back center brace is pressure stamped, or "branded" in a football shape stating Sigma Guitars/Made in Japan/For/C. This may be due to them being built in several Japanese factories at the same time with no coordination in the serial numbering system.However, while some models lasted the entire run from 1970 through 1983, others did not and were only offered for a limited number of years, so that most models' construction dates can be narrowed down to a reasonable range.75XXXXXX possibly equates to a build year 1975.) It is widely assumed by owners and Sigma historians that this is correct, though C. These instruments were constructed using preformed and sometimes partially assembled imported parts, built or completed in the C. Martin factory in Nazareth, Pa alongside the regular production line Serial numbers for Sigma guitars built in Korea and Taiwan are perhaps meaningless, though again some seem to indicate the year of manufacture (e.g.81XXXXXX.) Since we know these instruments were manufactured from 1984 through 2007 in these two countries, it is safe to assume that a serial number beginning with 81XXXXXX was not produced in 1981.1970" underneath in a smaller block font, in the familiar Martin headstock decal form. re: My own first Sigma, a DM12-5, which I purchased new in mid-1977 (I still have the receipt) had this second gen "Martin style" decal logo.It being a smaller, local store, the instrument may have been sitting there for a while before I acquired it.
The sigma symbol is often described as a "sideways M."Sigma's made in Japan from 1970 through 1979 used a paper label to identify the model and serial number of the instrument.For example, serial numbers on the earliest DR-7's start with 4 digit numbers on through 5 digit numbers.One Sigma DR-7 owner stated "I have an old Sigma DR-7 Guitar....s/n 6860.I bought it new in 1970." Further, DR-7's with a four digit ink stamped label serial number and a zero fret strongly suggests a very early build date.Some early 70s Sigma guitar serial numbers started with 7* suggesting the 197* build date (e.g. "Sigma-Martin USA" guitars built in 19 had serial numbers 900,001 to 902,908.In 1980 the paper labels were discontinued and the inner back brace was "branded." With the move of production to Korea in 1984, paper labels, this time with a fancy border, were reinstated, although some early 1984 models still retained the back center brace stamping.