http://www.forgottenweapons.com John Browning's Auto-5 long recoil shotgun was the first mass-produced semiauto shotgun, and would eventually become the second best-selling semiauto shotgun in the world (not bad for the first one to hit the market). It was patented in 1900 and initially manufactured by FN in Belgium, with Remington starting production in 1905. This particular one is in 12 gauge.