“Day 51: This is a 6 note set issued on May 15th, 1921 by the city of Bielefeld. Each of the 6 notes in this set have a denomination of 50 Pf.
On the lower left hand of each note is a letter(s) that spell out the word RÜBCHEN when all 6 notes are placed in order. Rübchen is German for turnip—a vegetable that played a key role during the time of famine in Germany.
The catalog value for this complete set of 6 notes is around $8 - $10. Here you can find more info about this set and others.”