Advertising card depicting Style 5-K ukulele, 1926

The early part of the 19th century saw a rapid rise in the popularity of the ukulele. C.F. Martin & Co. developed a mahogany ukulele in the mid-teens and a koa wood style in 1920. The company estimates it made more than twice as many ukuleles as guitars during the 1920s. The style 5-K was produced from 1922-40. It featured a curly koa wood body, an ivorioid bound top and back with abalone trim, a 17 fret ivorioid bound ebony fingerboard, an ivory nut, and patent pegs. C.F. Martin & Co., founded in 1833 and headquartered in Nazareth, Pennsylvania, is the world's oldest surviving producer of guitars and the largest producer of acoustic guitars in the United States.