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 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.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.This is understandable since the Martin customer service department now responds to individual inquiries stating "all" Sigma's had laminate back/sides with solid tops, while Sigma catalogs from the early 70s list the back/side wood as solid.To complicate matters further, in the 70's Sigma produced a line of guitars clearly identified by Martin, at that time, as having laminate backs and sides: model numbers starting with 52S, e.g., 52SDM-5, 52SDR-7 and 52SGCS-7.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.
" is best answered "That depends on the year and model." It is safest to assume that the Sigma in your hand is made of laminate sides and back, however it has also been said that some of the earliest Sigma's were made completely of solid woods.
The earliest examples had a plain black on white inner paper label giving the model and serial numbers.
Later one's (c1972 onward) had white labels that had gold lettering with a border, often reddish-brown or purple in color. followed by an ink stamp of the model number, and prefixed by the serial number assigned to the instrument. L-R as seen through the sound hole: Serial number, "Brand," Model number.) Serial Numbers Sigma serial numbers do not provide an indicator of the year in which a particular model was built.
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.