“Day 21: This is a set from Altrahlstedt, issued in 1922. These particular notes are the less valuable variety which include overprinted text and a signature stamp on the back side of each note.
The set consist of 5 notes, with denominations of 1 Mk, 2 Mk, 5 Mk, 10 Mk, 25 Mk.
The catalog value for this set is around $10. The version of the set without the overprint on the back is worth $500+! Here you can find more info about this set and others.”