I recently purchased an old Criterion Cutlery straight razor from a local antique shop. It has the markings: Hollow Ground, Fully Warranted. Then on the base of the blade it reads "Criterion Cutlery Co. Germany". If anyone can give me any clues on where to find more about it or how much it is worth, or even just how old it COULD be, Please let me know. Any help at all is appreciated.