The Oliver Diston Company was a music retailer with branches in New York and Boston. The Ditson company and was one of Martin's largest customers, selling guitars and other instruments, including many mandolins. Some Ditson branded guitars were made by Martin. The early ones (made around 1917) were stamped with "Olver Ditson Co. Boston, New York" on the back of the headstock, later ones have both Martin and Ditson stamps. The final batch (made from 1923 to 1930) have Martin serial numbers. Besides the "Ditson Model" Martins, Ditson sold regular Martin models, stamped with the C. F. Martin name. Some of these regular Martin models were also sold by Ditson with the Ditson stamp on the back of the headstock and/or on the inside center strip. And many other models, such as the Empire, were made by other manufacturers for Ditson.  So an instrument with the Ditson stamp does not necessarily mean it was made by Martin.

Source: Vintage Martin Ditson page (20 March 2017)
Source: Vintage Guitars Info - Martin (20 March 2017)