I bought a Sigma DR-11 new in Cookeville, TN sometime in 1979 when I was in college. It has mother of pearl inlay around the face of the guitar as well as the soundhole, and oblong hexagonal mother of pearl inlays on the fretboard. It also has the three piece back with a decorative inlay on the back that pieces the three pieces together. I too have been told my guitar model didn't exist. I am thankful for the information I have found on this website, and hope to learn more. I believe the name of the music store was Middle Tennessee Music where I bought this guitar. I had just come in on a delivery from Nashville. I was told by the saleman at the store that this guitar was especially made for a Guitar Show in Nashville. Being in college I had to go borrow the money and almost lost the guitar to any buyer before I got back to the store. I believe I paid around $350 with a hardshell case. I still have this guitar today and treasure it. Although I collect them and have over 30 guitars, this is still one of my favorites and is the one I have owned the longest. I will never sell it. I use only light gage strings on it and the neck is still straight as an arrow after over 27 years.
Sephearl