Well, not really a pin but a keychain. It shows the weapon of Olkusz on a piece of wood.
Olkusz is located south of Poland and contains 36.000 inhabitants. Olkusz is called ‘Silver Town” because of the large amount of silver that was found and mined here.
3rd. of July 1940 is known as ”Bloody Wednesday Of Olkusz”. A German police unit gathered all Jewish men over 14 and they were then subjected to hours of bullying sadism, forced to lie face down in the city square and beaten if they moved. Three men died from the beatings. The event was absolutely unexceptional as regards the treatment of Jews in Poland, but on this occasion however photographs, taken by at least one German present, survive.
In total over 3 million Jews died in WWII in Poland.