Conn patented his rubber-rimmed mouthpiece in 1875 (with patents to follow through 1877) described as "an elastic face a rubber rim where the mouthpiece comes in contact with the lips, the object being to prevent fatigue and injury to the lips." About this time Conn met Eugene Victor Baptiste Dupont (b. Paris ?May 1832; d. Washington, D.C. 26 July 1881), a brass instrument maker and designer and a former employee of Henry Distin of London. In January 1876, Conn joined with Dupont under the name of Conn & Dupont, and Dupont created Conn's first instrument, the Four-in-One cornet, with crooks allowing the horn to be played in the keys of E♭, C, B♭, and A. By 1877, Conn's business had outgrown the back of his grocery store, and he purchased an idle factory building on the corner of Elkhart Avenue and East Jackson. Conn's partnership with Dupont was dissolved by March 1879, but he was successful in attracting skilled craftsmen from Europe to his factory, and in this manner he expanded his operation so that by 1905, Conn had the world's largest musical instrument factory producing a full line of wind instruments, strings, percussion, and a portable organ. Conn partnered with Albert T. Armstrong, Joseph Jones, and Emory Foster to manufacture a twin-horn disc phonograph called the 'Double-Bell Wonder' that was produced in two iterations briefly in early 1898 before a lawsuit by the Berliner Gramophone Company caused production to cease. Brick-red 'Wonder' records were also pressed for the 'Double-Bell Wonder' talking machine by the Scranton Button Works from pirated Berliner masters. Fewer than fifty 'Double-Bell Wonders' were produced of both iterations combined.