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 902,908.75XXXXXX 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.The early 70s models (1970 -1975) can be distinguished by a headstock logo consisting of the single word SIGMA surmounted with the Σ symbol (the Greek letter sigma), in mother of pearl.
The issue of whether or not Sigma guitars are solid wood or laminate wood has been a source of controversy and confusion for many years now.While I cannot be absolutely certain of the year it was manufactured, it was certainly by, or prior to 1977.High end models such as the D-10 Anniversary model have the "Second Generation" logo inlaid in the headstock using mother of pearl. Some of these guitars also had the "Est 1970" instead of the C. Martin & Co.," but in a slightly different block font (fatter/wider) from the original 2nd gen instruments.Dreadnought models DM-5 and DR-7 are the most common early Sigma guitars until the late '70's.D for dreadnought, R for rosewood, M for mahogany and the number denoting the grade of wood, 5, 7, 9, 11, 15.Construction moved from Japan (1970–83), to Korea (1984-93/94), and finally Taiwan (1993–2007).In 1980, model designations were added to capitalize on Martin model numbers: the DM-18, DM-19, DR-28, DR-28H, DR-35, DR-41, and DR-45.The DR-28 was manufactured in Japan, Korea and Taiwan while the SDR-28 and the SDR-28H appear to have been manufactured in Korea and Taiwan only, starting in early 1984.The DR-28 was of a solid Spruce top with laminated Rosewood sides and back while the SDR-28 and SDR-28H was made with a solid Spruce top and solid Rosewood sides and back.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.