first gen. colt 45 made in 1902

Hello... I have a colt 45 that belonged to my grandfather. It is in good condtion with all matching serial no. It is nickle plated. I took it to a gun smith and he said I had a valuable gun. Does anyone know how much it could be worth.It is made in 1902 because of serial no. I looked up.

Need really good pictures....

There's certain things that can make a particular gun jump in price but it's mostly about ORIGINAL condition, condition, and condition. Unfortunately here's also a significant (at least noticeable) price difference between pre and post 1899, collectors are well just collectors...