You have a K-Frame revolver from 1956. That is before Model Numbers were marked on the frame under the cylinder yoke. I can't read the caliber marking in your photo of the right side of the barrel, but if it is marked 38 Special, I would guess your gun to be a Combat Masterpiece, later to be called a Model 15. I am no expert, but I'm sure one will be along soon to give you a correct, definitive answer.
