It's very important to note that your Scovill backmark has no circle-of-dots nor an indented ring-groove around the shank, nor around the outer edge of the back (outside the backmark's letters). he McGuinn-&-Bazelon book on button backmarks shows (in a photo) a "no rings" (nor circle of dots) backmark almost identical to yours (except it has a dot at the beginning and end of Waterbury). The book says that back dates from 1870 to 1890.
Now, all of that being said, your button's exact back (ringless, with a dot at the start and end of Waterbury)is shown on a World War One era US Army "Great Seal" button in the photo below.