Supertone was a stencil brand of a marketer that sold horns made by Conn and Martin in the 1920s. Stencil horns were modified versions of the horns that the manufacturers sold under their own names. The modifications were usually to meet the cost criteria of the marketer. They are the equivalent of student/intermediate horns, but are often good players that sound very close to the manufacturer-branded horns they are based on. The patent date is not the date of manufacture. The patent in question was for the process of drawing the tonehole chimneys out of the body as opposed to soldering them on. Martin used soldered toneholes. Your horn was in all likelihood made by Conn. The "P16661" is the serial number. The "L" stands for "low pitch." Prior to World War II, saxophones were sold in low pitch and high pitch models. The low pitch horns were tuned to A=440 Hz, which is the standard used today. A horn marked "H" is a high pitch model. High pitch horns cannot be used to play to modern tuning standards. What exactly do you mean by the toneholes having "no radius?"