Martin dating guitar
These guitars are thoroughly inspected and prepared by Martin craftsmen at our factory and carry a limited lifetime warranty. White binding on body (w/b/w/b/w.) Rosewood overlay on 1st generation "Spatula" headstock (Sigma w/Σ logo.) Headstock and fretboard are single-bound in white. Laminated rosewood sides and 3-piece back, ala' D35.
Other Sigma instruments included mandolins, banjos, acoustic and electric Bass guitar basses and solidbody and Semi-acoustic guitar|hollow body electric guitars. White/pearl binding on body (w/p/w/p/w.) Rosewood overlay on 1st generation "Spatula" headstock (Sigma w/Σ logo.) Headstock and fretboard are single-bound in white.
Bridges and tuners may have been installed, as well final sanding and finishing before strings were installed and a final set-up was done. Serial numbers for Sigma guitars built in South Korea, Taiwan and Indonesia are perhaps even more meaningless, though again some seem to indicate the year of manufacture (e.g. Adjustable rosewood bridge to approximately 1975, non-adjustable thereafter.
Because more than 30% of the work was completed within the borders of the United States, Martin was legally allowed to designate them as Made in U. 81XXXXXX.) Since we know these instruments were manufactured from 1984 through 2007 in these three countries, it is safe to assume that a serial number beginning with 81XXXXXX (which I have personally seen) were not produced in 1981 and that these serial number 'indicators' are not to be trusted.
This may be due to them being built in several Japanese factories at the same time with no coordination or tracking in the numbering system.
For example, serial numbers on the earliest DR-7's began using 4 digit numbers on through 5 digit numbers, with some early 70's models (c1972-c1975) along the way with the unusual 7*0XXXXX, 8-digit system. Adjustable rosewood bridge to approximately 1975, non-adjustable thereafter. All known Sigma guitars have laminated sides and back wood. This is understandable since the Martin customer service department now responds to individual inquiries stating "all" Sigma's had laminate back/sides, while Sigma catalogs from the early 70s list the back/side wood as "Matched." (edit: "Matched" does not mean solid, but is a careful marketing nomenclature for laminate to confuse potential buyers.) In the 70's Sigma produced a line of guitars with model numbers starting with 52S, e.g., 52SDM-5, 52SDR-7 and 52SGCS-7. While it was thought at one time that these were somehow 'special' and had solid tops, based on current research and scholarship, an emerging school of thought dismisses this notion. The Back Brace Brand: From 1978 through 1983; 1978 being a transition year, one might find the center back brace is pressure stamped, or "branded" in a football shape stating Sigma Guitars/Made in Japan/For/C. During later Korean made years (c1990,) Sigma transitioned back to paper labels and they stayed that way until the end of production in Indonesia in 2007. All other text was printed in black ink, or stamped on in ink by the manufacturer (model and serial numbers.) 5-digit, or 8-digit serial numbers. Being a mid-year change, some continued on with the "Purple" label, though with the new serial number designation preceded by an "S" or an "E" This is prefixed by the serial number assigned to the instrument and followed by an ink stamp of the model number. L-R as seen through the sound hole: Serial number, "Brand," Model number.) The serial numbers on these instruments were often preceded by the letters S or E; e.g. It is currently believed that this transition was complete by 1979.