Dating my sigma guitar
Later first and second generation Sigma guitars were clearly made of laminate wood for the back and sides, with the exception of several Limited Edition models, such as the D-10 Anniversary guitar.Other Sigma instruments included mandolins, banjos, acoustic and electric basses and solid body and hollow body electric guitars.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 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.
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 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.All other text was printed in black ink, or stamped on in ink by the manufacturer (model and serial numbers.)From 1980 through 1983, the end of Japanese production, the back center brace is pressure stamped, or "branded" in a football shape stating Sigma Guitars/Made in Japan/For/C. This may be due to them being built in several Japanese factories at the same time with no coordination in the serial numbering system.