Preserving A Piece of History

Below is an 1873 Calvary SAA mfg in 1875 and it obviously looks that old, which I like. What I don't want is the rust that might progress over time, unless I do something to preserve the gun. Not looking for a new appearance, though Uberties are pretty. Like to knock off the rust that's there, without damaging patina. For example, I once saw a Calvary SAA that had been sent back to Colt in the 50s for some "minor repair and restoration". Colt stamped the gun appropriately and when they were done, it retained a pleasing patina, but the rust was largely gone. Does anyone know who does that kind of work today? Might be more difficult than a ground up refinishing and restoration. I don't know. Appreciate your thoughts and suggestions on preserving relatively rare and historical old guns like this. Thanks,
LarsAK