This is one I need to research some more once the 2019 site reload is complete. My first impression is that this looks a lot like the D.F. Briggs building on the Mill St side. Looking at a plan from 1895 however identifies this building being closer to downtown with the Briggs factory next to it. They may have been of the same design and built at a later date, again I don’t know for sure. None of the buildings on the Sanborn diagram seem to have the 2 bump outs at the ends with the central tower feature.