Town Historian Vera Schmidt told Reuters she is convinced the debt slip is still valid, even though it has no seal.
In 1893 there was a debate in which the document was examined and the writing was determined to be authentic, Schmidt said.
Mittenwalde is situated 30 km from southeast Berlin and has a population of 8,800. The repayment of debt would be a significant fortune for the town.
Even if Berlin were willing to pay back the debt, it would cause a significant dent as the German capital is already close to 63 million euros in the red, according to a report released by its finance administration in June.
This case shows that debts always catch up with you, no matter how old they are, Finance Senator Ulrich Nussbaum told the Berliner Zeitung paper.