Thank you for the great description and the one photo. Please add one photo of the whole set and one photo of the mark on one piece. By looking at this mark and the shapes around the symbols and letters, I can date the set and determine the maker for you, which helps in the valuation as well.
Use the Add Files feature on your screen to add pictures. If you are unable to photograph the marks clearly, you can do a rough drawing and photograph that. In order to be sterling (925) there should be a lion and a letter in their own shapes near that maker mark.
I can finish my answer for you once I have all of this additional information.