The Sigma brand was established by C.F. Martin & Company in 1970, as a way to introduce Martin models to the more budget-minded beginning player. Although Martin continues to offer quality instruments at bargain prices under the Sigma name, the desire to offer a Martin model to every player, regardless of budget, at every price level, led to the creation of the Sigma-Martin brand (1981) and the Shenandoah brand (1983).

This is an acoustic-electric guitar, made in Korea to the specifications of C.F. Martin & Company. The finish is clear lacquer over red stain on a solid mahogany top, with solid mahogany back and sides. A bound rosewood fretboard caps the one-piece mahogany neck. Abalone inlays adorn the rosette and peghead. This model also features an unusual curved back.