Quoting from "American Military Button Makers and Dealers; Their Backmarks and Dates" By 1835 the firm was R & W Robinson and continued under that name after Richard Robinson died in 1838. The Robinson firm lost most of its civilian button trade in the 1840s & was bankrupt by the middle of the decade.
The States got the technology to make those type buttons around 1820 and by 1840 that type of button was falling out of favor. New technology was now producing mother of pearl and other type buttons. So it should be safe to say your button was made from 1835 until the mid 1840s.
And by the way, that is a very nice specimen, the backmark is particularly nice.