Among german stamps 20,000,000 German reichsmark stamp was issued on 1923-10-28 during the inflation period. This emission had 2 variants that you can see here. Type of printing was typography.
German stamps during inflation period had a lot of enormous values because of the economic disaster. It is well known that the government was forced to print more money and the value of the mark begin to fall dramatically.
Workers were paid a few times each day having off time to spend the income before its value vanished. They say that during the year of 1923 a piece of bread worth billion of marks and markets were empty.
Between 1921-1923 about 200 varieties of german stamps were issued. The overprinting method was actual because the economic crash and the post office could not design new german stamps to keep up with the inflation.