Approximately 2,500 Camp Perry pistols were marketed by Colt between the years 1920 and 1941. This unusual model was created by replacing the 6-shot cylinder of the .22 Officer’s Model Target with flat “cylinder” containing one .22 cal. chamber. Camp Perry, Ohio is the site of the annual National Rifle and Pistol Matches.

https://www.nramuseum.org/guns/the-galleries/innovation,-oddities-and-competition/case-25-camp-perry/colt-camp-perry-single-shot-target-pistol.aspx