Missouri’s secretary of state has certified a ballot question that could let voters repeal the state’s 0 gambling loss limit in November. Increased revenue estimated from unlimited play could boost state gaming taxes 5 million a year or more, especially with the rate raised to 21 percent from 20 percent under the measure. It also scraps required casino I.D. checks unless needed to prove players’ ages, and it caps the number of casinos allowed at 13. That mix of issues could lead to a challenge of the referendum’s constitutionality before the election. Meanwhile, the Missouri Chamber of Commerce and Industry, representing 3,000 companies, has endorsed repeal of Missouri’s 0 loss limit. The referendum has yet to be certified for the ballot. Casino operators Ameristar and Pinnacle have each put .2 million into the referendum effort.