I have a CD 281 Hemingray No. 2 High Voltage with both prism and stamp embossing on the same unit. The patent date on the rear is prism as is the HEMINGRAY on the front but the No. 2 HIGH VOLTAGE under HEMINGRAY is stamp. There is no trace of a blot out or a rework of the mold. Is this unusual? Has anyone seen different examples of this?