Guitars made in Taiwan have a different headstock decal: "Sigma Guitars" on top with a miniature version of the "C. The paper labels for model/serial number identification had also changed again, this time with a fancy border and the word "Sigma" or "Sigma Guitars" in gold ink.
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.
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.
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.
The answer to the question "Are Sigma guitars solid wood or laminate?