This new Authentic is constructed the old way - with hide glue, throughout, and historically-accurate detailing confirmed by using a CAT scan machine located at the Smithsonian Institute. Based on a 1939 D-18 in the Martin Historic Museum, this guitar features genuine mahogany back and sides, an Adirondack spruce top, using an authentic circa 1939 bracing pattern. Period-correct "18" Authentic-style appointments, with an Authentic neck barrel and heel, complete this piece. Martin’s new VINTAGE TONE SYSTEM^® (VTS) is employed for the top and braces. The new Martin VINTAGE TONE SYSTEM^® uses a unique recipe that is based on the historic torrefaction system. The VTS acts much like a time machine in which Martin can target certain time periods and age the top/braces to that era. This focused method allows Martin’s craftsmen and women to recreate not only the pleasing visual aesthetics of a vintage guitar, but also reproduce the special tones previously reserved for vintage instruments.