A 50.000 Mark German banknote issued in 1922 is not particularly valuable as a collectible, and it has no face value as an obsolete form of currency. The period in 1922 saw the rise of inflation and hyperinflation in Germany as it struggled to pay reparations for its role in WWI.
After the assassination of the Foreign Minister in June of 1922, German currency began to decline. By the end of the year, a single American dollar was worth 2000 Marks. The rate further deteriorated the following year until it reached an exchange rate of 1:2,000,000.
Currency was printed in greater and greater quantities. A firm in southern Germany printed a 50,000 Banknote with the inscription, "If coal is even more expensive, feel free to use me as fuel."
Since the banknote is readily available, it is worth approximately 2 to 10 Euros, depending on the condition.