Dating old square nails like yours is not a certainty because they were produced in this manner from 1830 onward. The best way to ascertain a "date range" would be by context. What else was found at this site and what level of strata was it found in relation to other datable artifacts or even any research of the home's age that occupied the site. Looks a lot like ones I dig from 1870-1890 period house sites though, if that helps. Electrolysis is great, wait till you get an unknown in your tank, that gets exciting as you see it unwrap.