In 1921, Germany began issuing this set of definitives featuring numerals and depictions of various German laborers.
The first value released (3 M) was released on 29 December 1921. The remaining values were released in 1922.
The 20 M value can also be found with inverted burelage. Due to the design of the stamp, this can be very difficult to detect — the easiest manner is to observe the pattern of the burelage in the corners of the design. Below is an image of the burelage pattern on a normal 20 M stamp, with examples of the corner patterns found on the normal variety.