The Hunter One-trigger was not cataloged until 1904 (not 1892), although some guns featured factory fitted Lard patented single triggers as early as 1901-1902 based on period advertising. After Hunter made the single trigger option available, existing guns were regularly factory retro-fitted with the Hunter One-trigger for a cost of $25. The Grade 3 Syracuse Smith on the web site has a retro-fitted Hunter-One trigger; and, as Researcher has pointed out already, the Grade 6 has an after-market Miller single trigger, which was very popular on vintage double guns after its invention and can still be purchased new today.