@en|Scanning of a May 1957 [[Sheaffer]] advertising for a [[Snorkel Pen]]. Published on ''The National Geographic Magazine''. Retouched by the author for a better sharpness. Date from cover. | @en|Scanning of a May 1957 [[Sheaffer]] advertising for a [[Snorkel Pen]]. Published on ''The National Geographic Magazine''. Retouched by the author for a better sharpness. Date from cover. |