This guitar is a Sigma E-18, solid body, electric guitar made by Martin's Japanese division. I don't actually know whether it was made in Japan or in the US. I have a Sigma Acoustic and my understanding was Martin set up the Sigma division in Japan to produce high quality, low cost guitars. But these electrics are more of a mystery. I'm guessing they were designed in the US at the Pennsylvania Factory and manufactured in Japan. If you have more information about this guitar please let me know. The dimensions are 40" long by 13" wide.
This Sigma is a very early model in the run; the serial number is 0000068. These guitars were designed by Dick Boak at Martin. Martin issued a very similar electric guitar with variations on the pickups and controls. This one has "CF Martin" on the tuners along with Sperzel. Presumably they were custom designed tuners for Martin made by Sperzel. These electric guitars were made from 1978-1980. The neck is straight and all the electronics work properly. I believe it to be completely original but I've never seen another Sigma model so it's hard to tell. There's one dent on the top of the body near the neck pickup (you can see it in the photo) and another slight dent below it. Otherwise, the guitar's in pretty clean shape.
As far as tone goes, this guitar is a serious rocker. The pickups have a real bite in all three modes. I think it'd work best for garage rock or hard rock. When I first got it I thought it had active pickups because they're so hot and overdriven. But I opened up the rear cavity and there's no battery. The bottom position on the toggle gives that Free's "All Right Now" Les Paul-type distortion, the middle is a bit more muted but still has a biting, edgy distortion, and top position gives a smoother, brighter tone with a tinge of distortion. If you roll back any of the volume or tone knobs slightly it cuts the distortion significantly. Also, if you roll the tone knobs almost all the way to the muted position it gives a much smoother tone without muting the entire tonal range. There's really a lot of tone variations on this baby! The neck feels great. The action is set fast. It's really lite for a solidbody guitar. It's ready to rock!