This map was drafted by Sigardur Stefansson of Iceland in 1579. The original has been lost. The map on the stamp is based on a copy made by Theodore Thorlacius in his Compendiosissima Descriptio Chronographica, Topographica & Chronologica published in  1669. It expresses the ancient idea that land surrounded the ocean, instead of the ocean surrounding the land. It embodies information which existed in the Skåholt monastery in Iceland at the time the map was drawn. The map locates place names by degrees of latitude, which allows us to identify the contemporary headlands and bays. It was another century before the accuracy of this map was improved on.  

     If you look closely at the map you will see alphabetical references. They provide an index to the various features of the map.

A This is where the English have come and has a name for barrenness, either from sun or cold.
B This is near where Vineland lies, which from its abundance of useful things, or from the land’s fruitfulness, is called Good. Our countrymen have thought that to the south it ends with the wild sea and that a sound or fjord separates it from America.
C This land is called Rüseland or land of the giants, as they have horns and are called Skrickfinna (Finns that frighten).
D This is more to the east, and the people are called Klofinna (Finns with claws) on account of their large nails.
E This is Jotunheimer, or the home of the misshapen giants.
F Here is thought to be a fjord, or sound, leading to Russia.
G A rocky land often referred to in histories.
H What island that is I do not know, unless it be the island that a Venetian found, and the Germans call Friesland.

Kirsten A. Seaver, "Renewing the Quest for Vinland: The Stefansson, Resen, and Thorlaksson Maps," Mercator's World September/October 2000, pp. 42-49.