It commemorates the Battle of Prague 1757. There are many medals of Frederick the Great and his battles against the Holy Roman Empire, he refused to accept Maria Therasa as Empress, notice she is called Bohemia (as in Queen) on this medal. He was surrounded by enemies the Austro-Hungarians, France, Sweden and Russia. England supported him with money and some-times fought on his side (Part of their European Balance of Power strategy or keeping France occupied elsewhere!). If you want to learn more google: Frederick the Great, Salic Law, Pragmatic Sanction, Holy Roman Empire etc.
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