Welcome to the forum. It sounds like a Colt Model Three-Fifty-Seven, which is roll marked on the barrel "COLT 357". Under that is 357 Magnum Ctg. a typical Colt marking meaning 357 Magnum Cartridge which is the caliber and the fact that it a cartridge firing revolver. Colts did not have model "numbers" in those days. They were made from circa 1953 to 1961. They were available with 4 and 6" barrels. They were indeed pre-Pythons, being the first I frame revolver. The I frame characteristic is a frame mounted firing pin. It is said that approximately 15,000 were made. There are several previous threads about them on rthe forum, but the search engine does not deal with "357" as a target. Try three fifty seven. Here is one for starters: https://www.coltforum.com/forums/colt...57-magnum.html.
And a 1954 catalog page:
And a picture: