In 1950, Monaco issued a small series of coins including two with a knight on horseback. Prince Rainer III held at least 11 different Knight Grand Cross titles, so perhaps that is the significance of the knight on this coin. I am pretty sure it doesn't relate to the beginning of his family's 700 year rule of Monaco, since that was achieved by Francesco Grimaldi dressing as a Franciscan monk to sneakily capture the fortress back in 1297.
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