This was Martin's first official 12-string model (essentially ended production 10 years after its introduction in 1964(?) I think) and it shared the original (Ditson) dreadnought body shape with a longer upper bout and round corners, more centrally-located bridge, and 12-fret neck join. It's essentially the same guitar as the "original dreadnoughts", save slightly heavier bracing and a larger slotted headstock to accommodate the tuners.After setup, cleaning, light fret dress, etc. this guitar plays really really nicely and has that big sound you'd expect of a Martin, made rounder and fuller by the 12th-fret join. 1 7/8" nut just like the original dreadnoughts... though for a real purpose here, as it gives perfect spacing for the extra strings.""