Two architectual paintings by same artist.

 I have two nice architectural paintings, I believe are lithographs. I think they are water colors, but I don't know for sure. The artist signed on both is MARC. There is also a C with a circle around it in the bottom corner of both paintings and also another circle with a ST/F (in between two horizontal parallel lines) in it. They are very nice paintings. I believe they are in the original frames. The frames have some water damage around the outside edge. The actual paintings have not been damaged, but if they are original frames, should I re-frame them? How old are these paintings? What type of paintings are these? Are they lithographs? What is the value of these two paintings? Thank you for your help..

Poor