About the Rapidograph pen: Oceanographers created their cartographic masterpieces on mylar sheets rather than paper. Being dimensionally stable, clear or translucent mylar sheets were used to overlay charts in the survey control center while conducting surveys. These records  (a/k/a "boat sheets") of the ships' track and position fixes along with depth recorder traces and computer printouts were the raw materials for the finished product, navigational charts. While these intermediary sheets may have been pencil drawn, the NAVOCEANO guys did their finish work in ink. The pen of choice was the Koh-I-Noor Rapidograph. In the 1960s these were expensive finely fabricated precision pens from Germany. A set of these would produce various line widths, indicated by a color code on the pen caps. A Rapidograph drew "india ink" up from a bottle through the cylindrical point into its ink reservoir with its internal plunger. A very fine wire inside the cylinder kept the ink flowing to the point. They were are a bit hard to keep clean if not in frequent use and worked better on mylar or hard surface paper. They were not really suitable for normal writing. In these days of CAD drafting and electronic charts all this sounds anachronistic. Today the Rapidograph and other "technical pens" are more often used by graphic artists than draftsmen. (By Site Admin, October 3, 2020)

This article appeared in the International Hydrographic Review (Monaco) vol. XLVI No. 1, dated January 1969. It can be found at: https://journals.lib.unb.ca/index.php/ihr/issue/view/1811..