A rare treasure, the Martin D-45 Dreadnought acoustic guitar has only been made in small handfuls of fits and starts over the past 80 years. Fewer than 100 D-45s were created between '33 and '42, giving them the title of legendary, holy grail acoustic. Although the D-45 was brought back in 1968 and has been in continuous production since, so few are made each year that the D-45 stays relatively static in price and collectibility factor regardless of when the instrument was made.