These are nice large silver coins from the Grand Duchy of Luxembourg. (Luxembourg is located between Belgium, Germany, and France.) They are made of 75 percent silver and have a total silver content of 0.323 troy ounces. Multiply that number by the price of silver and you have the base value of the coin.
For instance, using kitco.com, today's silver price is about $17 US dollars per ounce, so the base value of your coin is 17 x 0.323 = $5.50.
Only if your coin is in really good condition will it be worth more than base value. Here are some approximate add-on values:
worn: add $0
average circulated: add $5
well preserved: add $20
fully uncirculated: add $40
Adding these values to the base value gives an approximate catalog value. Use our Important Terminology page to understand how to interpret catalog value.