Self-regulating cold cathode three electrode glass x-ray tube with duplex gas auto regulation, based on a design developed by C. H. F. Müller in Germany. Inscriptions read “MADE BY / THE FRIEDLANDER CO. / Chicago / U.S. PATENT No. 725331 / German Patent No. 145788 / Canadian Patent No. 85281 / 1121.”
Ref: Theodor Friedlander, “X-Ray Tube,” U.S. Patent 725,331 (April 14, 1903), assigned to R. Friedlander & Co.