c. 1850s C.F. Martin & Co. Custom
This guitar is an early example of a modern acoustic guitar and one of the first X-braced guitars. Christian F. Martin (namesake and founder of C.F. Martin & Company) was credited with popularizing this style in the 1840s. X-bracing consists of two wooden braces in an X pattern under the soundboard. This was a revolutionary advancement in how guitar bodies were constructed, which allowed acoustic guitars to produce a more powerful sound. The X-braced innovation also allowed for the use of sturdier steel strings instead of gut strings.
Described in "The Chinery Collection: 150 Years of American Guitars" as: "This may be the first X-braced steel-string guitar Martin made, and is therefore in my view the most important Martin I have in the my collection. In fact, I often wonder how music might have developed in a totally different way had Martin not come up with the X-bracing idea, which turned out to provide the perfect sound and tone for the later flat-top steel-string guitar."