This is my day for finding unknown stuff. I am assuming that this is a Cinderella as it appears to be an unofficial overprint on a Polish Issue. Is it a Propaganda Issue of some sort or does it fall into a category of revenue issues?
This is a propaganda label (NOT a postage stamp) directed at residents of the Upper Silesian region. lt was made during the post-WWI plebiscite era for an area which the victorious European allies wished to extract from Germany.
The label and overprint are of German manufacture. The label tells the Upper Silesian viewer that his/her currency and goods will be worth more if he/she votes for the area to remain German, rather than to become Polish.