GUILD produced the M-20 between 1958 and 1973. It was an all mahogany version of the folk favourite the Guild F-20 Troubador. The small concert-sized M-20 was one of the lowest priced Guild flat top acoustics of the period - it was even labeled the "Economy M-20" in the Guild 1963 catalog. This all mahogany body gave the M-20 a distinct tone: warm, dark and with note separation perfect for fingerstyle playing. From 1958 to 1961 the M-20 had the old (Gibson) style headstock - this was changed to the new Guild style in 1962.

Nick Drake is shown holding a Guild M-20 on cover of his 1970 album Bryter Layter, perhaps encouraged by this association with Nick Drake Guild reissued the M-20 in 1998 for a while and also recently issued a similar M-120 model.

Guild describe the M-20 as follows in their 1963 catalog:

A fine quality concert size guitar at an attractive budget price, made possible only by the most modern production facilities in Guild's enlarged plant. This lowest-price Guild offers most unusual value.  Has the fine construction and features for which Guild is famous, including Guild's fast-action mahogany neck with adjustable steel neck rod, finest rosewood fingerboard and pearl position markers. Honduras mahogany body is 13.75" wide by 18" long by 4.125" deep. Tortoise color pick guard, rosewood bridge, nickel-silver frets. Equipped with non-slip tuning pegs and Guild Strings.