Various, International Library of Technology… (1909)
“ The best knobs are usually solid; that is, cast in one piece, with the exception that the shank is inserted. Others are made in composite form, consisting of a steel interior shell, or frame, over which is tightly drawn an external section, or covering, of wrought-bronze or brass of substantial thickness. The completed knob, if properly made in this manner, is practically as strong as the hollow-cast knob and resists bruising or other injury.56. Glass Knobs.—The most expensive knobs made are those of cut glass with metal mountings. Several knobs of this kind are illustrated in Fig. ”
