The "registered" mark started in 1882, not sure how you could date it before or after 1900 though. Is there a maker's mark anywhere on the bottle, that might help...
Hello Mitch, Welcome to this place. Please do put up several good photos of your bottles. If it's a Root, it's gotta be post 1901. Chapman Root didn't get his plant built until November, 1901. http://visions.indstate.edu:8888/cdm/ref/collection/vchs/id/576
Yeah that's what I thought! So what would a pre 1900 biedenharn have different then mine? Would it say something different than root or have other markings?