POW camps in Germany used tokens as internal currency; that way, if the prisoners escaped, they wouldn't be able to pay or bribe local citizens with regular German money.
Google Translate can often be of assistance for items such as this. "Kriegsgefangenenlager" translates to "Prisoner of war camp".
Dulmen is a city in north-western Germany, not far from the Dutch border.
This website tells something of the story of the camp.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis