The 925 sterling silver mark indicates that the sterling silver item is composed of 92.5% silver and 7.5% an alloy, which is typically copper. The reason an alloy is added to the silver is because pure silver is soft. Adding other metals to the silver increases the hardness making it suitable for jewelry and medals. The use of the 925 mark in the US became a requirement in 1906.
At Rosa Mystica Medals all of our replicas are cast in sterling silver from a mold of the original antique medal. If the original antique does not have a 925 or sterling silver mark, then our medal, which is an exact replica of the original antique medal, will not have a mark. One way to test to see if the medal is made of sterling is rub it with a soft white cloth. If you see black marks on your cloth, you can be sure that the medal is made of real sterling silver. The black marks are a result of oxidization caused by any air exposure.