It's a long shot, but I have a family of Vance ancestors, including some William and John Vance's, from PA and NJ, about the same time as your Mary. In their case, the H. middle initial stood for Homan, after Rachel Homan, who married John Vance in the right time frame. Quite of few of these Vance's used the middle initial H. They were a family of Presbyterian ministers (at least 2 of them) who moved around PA and OH. One was even the Keeper of the Cemetery in Erie, PA towards the end of the 1800's. My grandmother was Caroline Homan Vance, daughter of the Rev Edward Dunn Vance. She was born in Kinsman, OH, he was born in PA. Gary Richardson