These 'Geuzenpenningen' were called the "Crescent moon of Boisot" because the Sea Beggars under the command of Louis de Boisot wore them on their clothing and banners during the lifting of the siege of Leiden in 1574.
The Protestant Sea Beggars displayed, using a crescent-shaped medal, with or without the motto "Liver Turcx dan Paus," their preference for the tolerance of the Ottoman rulers in Turkey rather than the Catholic oppression exercised by King Philip II of Spain. In addition to these medals, this motto was found in the songs of the Beggars and was also used during open-air sermons ("hagepreken").
The shape of the medal itself is the symbol of Islam and the Ottoman Empire.