Read further in the Wikipedia article, the first sentence in the 'History' section is > In 1987, Max Atchisson sold the rights of the AA-12 to Jerry Baber of M

Read further in the Wikipedia article, the first sentence in the 'History' section is > In 1987, Max Atchisson sold the rights of the AA-12 to Jerry Baber of Military Police Systems, Inc., Piney Flats, Tennessee Quoting the New Yorker in full >[...]he started producing, from start to finish, his own weapon: a fully automatic shotgun called the AA-12. it is obvious that he was the first to produce a mass market ready model. The article doesn't claim that he invented it.