Under the direction of the Swedish Admiralty Johan Månsson gathered information on the Baltic Sea; sounding is coastal waters, the location and shape of islands and shoals. In 1643 he was appointed the senior navigation officer. The following year his Sjobook, or Seabook was printed at Stockholm by Ignatius Meuer. Included in the book was his Sjokarta or  Sea Chart, based on the information he had gathered. The stamp reproduces this map in simplified form. The original chart has the long dimension east and west, and the physical detail, soundings, names and so on is not included on the stamp.

     The stamp below shows Månsson  holding a sounding lead and an hourglass. A ship's compass is at his feet. These were the instruments used in the 17th century for hydrographic surveying. They depict part of the cover of Månsson's Sjobook.
     The chart pictured on the stamp is not from the Sjobook. It was drawn by Johan Nordenancher in 1800, engraved by F. R. Akrell, and published in Gustaf af Klindt's Atlas No. 6, edition 16 (1805-1813). The stamp shows part of the chart of the island of Oerskaer in the north, the Graesoe Island, the Oeregrund Archipelago, the Aeland Sea and the waters to the north.

The information on these stamps comes from
Water Klinefelter, A Small Display of Old Maps and Plans,
Iowa City, Prairie Press, 1962, pp. 41-44,
Stig Goeransson, The Cartophilatelist 38(1993)100,
and 39(1994)22.