@en|Scanning of a 1955 [[Sheaffer]] advertising for a pen/pencil set of the [[Snorkel Pen]], ''Sentinel'' version. Retouched by the author for a better sharpness. Published on ''The National Geographic Magazine'', Vol.CVII, No. 5. Date from copyright note. | @en|Scanning of a 1955 [[Sheaffer]] advertising for a pen/pencil set of the [[Snorkel Pen]], ''Sentinel'' version. Retouched by the author for a better sharpness. Published on ''The National Geographic Magazine'', Vol.CVII, No. 5. Date from copyright note. |