Tonk Brothers was a Chicago based musical instrument wholesaler, established in 1893 by Charles J. Tonk (1856-1918). When the last of the Tonk family left the business in 1913, when it was taken over by Paul Moenning. In 1928 Lyon & Healy sold their Washburn brand name to JR Stewart and their wholesale distribution business to Tonk Bros. As a result JR Stewart made Washburn instruments for exclusive distribution by Tonk Bros. When JR stewart went bankrupt in 1930 Tonk Bros bought the Stewart factory as well as the Washburn, Stewart and Le Domino brand names from JR Stewart, but soon sold the Stewart and Le Domino names to Regal. Tonk continued to wholesale instruments from  various Chicago makers including Regal, Harmony, Kay and Stella.

Source: Washburn: Over One Hundred Years of Fine Stringed Instruments. John Teagle. 1995. Music Sales Ltd.

Source: Tonk Bros catalogs 1930s to 1950s