Generally, a backmark saying Scovills is from 1840-50, when that company used the name Scovills & Co. (It became the Scovill Manufacturing Company in late-1850.) But I have seen some 1820s/30s CUFF-SIZE (15-16mm) ONE-PIECE brass buttons with the Scovills (plural) name. Apparently, the company's full lengthy name in the 20s & 30s (such as JML & WH Scovill / Waterbury) was too long to fit on a cuff-size 1-piece button, so something short-&-simple like Scovills Extra was used. It seems most button scholars think Scovill was no longer making cuff 1-piece brass buttons in the 1840s, when the company name was Scovills.
In summary... I agree with Fyrffytr1, your find is from the 1820s/30s, despite having Scovills in the backmark.