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.
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.
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.
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.
Sigma identified their dreadnought and grand concert guitars as "Second Generation" when the headstock design changed to utilize a gold decal stating "Sigma Guitars" in script with "Est.
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.
in Nazareth, Pennsylvania to be inspected and adjusted by Martin personnel before going to an authorized retail store for sale to the public.
These inspections and adjustments were made in the "old" Martin building on North St.(c1865,) then known as the Import house.
The DM-5 and DR-7, as well as other early models continued to be built during this time as well.