The purpose was to cause dissent amongst the Nazi leadership and to help to build a perception in the German population that Hitler was a puppet and that Himmler was 'pulling the strings' in the Third Reich. Unfortunately, although some examples of the stamps were smuggled into Germany and used by agents amongst the foreign labour force, nobody in Germany seems to have noticed that there was anything wrong with the stamps! There is a good description of the operation in 'The Black Game' by Ellic Howe.
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