The Gibson L-0, introduced in 1926, was (along with the L-1) Gibson's first production flat-top acoustic guitar. Both the L-0 and L-1 were made economically: lightly braced, with thin woods and finishes. This light construction gave them a great tone but also made them less robust to wear and tear. The Gibson L-0 originally had a spruce top and maple back and sides, from 1928 onwards the top, back and sides were mahogany. The 19 fret neck originally joined the body at the 12th fret - this was changed to the 14th fret from 1932 onwards.
Although the L-0 was a production model guitar, they were hand made and there was considerable variability in the specifications - making it challenging to authenticate a genuine L0. For example the scale length varied from 24.5 to 25.25 inches and the neck profiles and top thickness also varied widely.
Source: James Einolf