Your find is what button collectors call a "Golden Age" 1-piece brass flower-button. Its backmark saying "Robinsons" refers to the Robinson brothers, who were button-makers in Attleboro MA from about 1813 through the mid-1830s, when the firm's name was changed to R&W Robinson. Specifically, your button was "most likely" made sometime in the early-1820s... because the Robinson brothers added non-brothers Jones and Draper to the firm, and their names are thereafter included in the Robinsons backmark.