The reverse shows the "Cologne monogram": S COLONII A - referring to Sancta Colonia Agrippina, the Roman colony that became Cologne.

This reminds me of Tyrker in "The Saga of the Greenlanders":
".. the news spread that a member of the crew was missing, none other than Tyrker the German. Leif was much disturbed at this, for Tyrker had lived in their household a long time and had been greatly devoted to Leif when he was a child. Leif angrily reproached his men, and made ready to start off with a search party of twelve. They had scarcely left the house when Tyrker came walking towards them, and he was received with great joy. Leif saw at once that his foster father was in high spirits. Tyrker was a short fellow, rather puny looking, with a prominent forehead and restless eyes in a smallish face; but he was handy at all sorts of craftsmanship.
Tyrker first talked a long time in German, rolled his eyes and made faces. They did not understand a word he said. After a while he changed over and spoke Norse. "I did not go very far beyond the rest of you, and yet I have some real news for you. I found grape vines and grapes!" "Is this really true, foster father mine?" said Leif. "Certainly it is true" he answered, " for I was born where there is no lack either of vines or grapes.""

There's this on Tyrker: http://en.wikipedia.org/wiki/Tyrker along with the thought that "the Norse word used in the saga is ‘vinber’. While this sometimes refers to grapes, it also translates into "wine-berry", and there is a long-standing Nordic tradition to make wine out of berries available." No shortage of berries at L'Anse aux Meadows! http://www.pbase.com/hajar/image/157196296 , but Tyrker's comment about vines doesn't seem consistent with this interpretation.

Adam of Bremen was also from these parts and he wrote about what he had heard at the court of Danish king Svend Estridsen (1047-1076) of lands west of Greenland: http://www.americanjourneys.org/pdf/AJ-058.pdf

As an aside, "Cologne was pillaged and razed by Vikings in 881–882, but Liutbert of Mainz assisted in rebuilding it."