Marie Louise was Archduchess of Austria, Princess of Hungary and Bohemia, Duchess of Parma, Piacenza and Guastalla, Empress of the French, and Queen of Italy (whew!). She married Napoleon in 1810. Numerous medallions were produced to celebrate the royal marriage. This is the most popular pattern.
These medallions were produced in various sizes and various metals. The most common is a 40 mm version in bronze, but there are also 27 mm and 15 mm bronze medals, as well as 32 mm silver medals, and 15 mm gold medals. Curiously, the size and composition do not matter very much when it comes to value, as the medals made with precious metal tend to be smaller than the bronze medals. What does matter is overall state of preservation and eye appeal.
MEDALS IN BRONZE, SILVER, AND GOLD:
worn, with lots of nicks, scratches, and stains: $100 US dollars approximate catalog value
average, with only a few detracting marks: $250
well preserved and in pristine condition: $500
Harshly cleaned medals are worth zero, or their weight in precious metal if gold or silver.
These are catalog values. Be sure to read out Important Terminology page which gives information about converting catalog values to actual buy and sell values.