I got the Sigma in 1988. Its a Japanese Martin. I probably play this one the most. Its got a rich, full bodied sound, and it plays nice. Sigma guitars were based on standard Martin models and were inspected at the Martin factory before going to market. While they discontinued this line in 2007 they still have a website. Mine is a DM-1B shown here.
Still my go to guitar. Love the sound and still love playing it. I do wish I had a smaller body guitar though for times when I don't need all the sound that this one projects.