Actually it took a bit longer to finalize the German-Polish border than 1919.
The plebiscite in Silesian area, wasn't held until 1921, where eastern part of Silesia went to Poland, western part to Germany and a small section of Silesia to Czechoslovakia.
However I don't know about the years when other plebiscites were held in other areas, that were thought to be separated from Germany?
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