Vikings: How to recognize a trading partner in the Viking period

http://www.waverijn.info/images/Info/Pages/17/Vikingen.htm Dutch source

Hail Vikings,

When I went to the Museum Meermanno the museum itself is about books. So when I got asked to go to a reading about graphic I didn´t expect the outcome of that reading. It was about the Chinese art Kai-awase Symbolon. those based on a love story where you get one-half of a shell and you need to find the other half. It is like memory but there is a difference both shells have different paintings inside. But enough about that. What has this to do with Vikings or trading I will tell you.

We know that in the time of the Vikings they had coins. In The Netherlands, they found half a coin or a quarter coin. This brings me to the story of the trading partner and the reading that I went to. At the reading, they told the coins had a real trading system at that time.

If you got a piece of land that you bought from a trading partner, and you have particular agreements with that partner, for instance, he kept the watch over your land while you were gone, how did he keep his promise to watch over the land? How did you know it was the right trading partner? How did they do that in those times?

The answer is given in this way: They cut the coins in half or quarter. If you got half or quarter a coin in your possession and the trading partner has half or three-quarter a coin it fits into a whole coin. So if you came back and you showed them the piece of the coin they could easily fit it. If it fits the agreement was that it was given back to you. 

This was also with family how to recognize family when not together or from another country it was your identification coin that would show if someone died or came to visit.