How old is this clock?

It is a Seth Thomas "Plymouth" mantel clock. I can't find a serial number, but it is an 8-day clock and the paperwork in the clock says that it is for a 4300, 4500, or 4600 series clock. It chimes a single chime on the half and the time on the hour? I know that it belonged to my great great grandmother, so I'm thinking late 1800's. Any ideas?