Guild M-20 - Concert Body Acoustic Guitar - Natural SatinM 20 Concert Acoustic Guitar Natural. Guilds iconic M 20 was the first guitar off the production line in 1967, when the company had grown so much that they relocated to a new factory in Westerly, RI. Nearly 50 years later, history has repeated itself in a brand new, state of the art facility in California. The M 20 is a concert size acoustic guitar built with solid mahogany top, back, and sides, informally nicknamed the Nick Drake guitar for its