Little Hawk, I used to own an M-36, which was the M-38's little brother. The differences were: (1) where the M-38 had a two-piece rosewood back, the M-38 had a three-piece rosewood back (like a D-35); (2) the binding on the M-36 was a little less ornate -- no abalone around the top (although there was an abalone ring around the soundhole), and no binding around the peghead, and (3) the M-36 had no volute on the neck/peghead joint (who knows why?). Both were great instruments, and it's too bad Martin doesn't make them any more. The M's were large guitars -- the lower bout was wider than a dreadnought -- but they weren't very deep, which means they were quite comfortable to hold. They were very responsive instruments, with plenty of low end but not so much of the boominess you get with a dreadnought. Of all the guitars I've owned and unloaded over the years, this is the one I most regret parting with.

I believe the M series was first constructed by putting a flat top onto the back and sides from an old Martin archtop. If I'm not mistaken, David Bromberg had a hand in its creation; I know he was playing an M-38 when I saw him back around 1980. Great guitar -- if you have to sell it, see if you can find it a good home.