Shottist nailed Iding a Cannon gun. numbered charge holes and C A N N O N spelled out on the weapon usually the cylinder.
That Aristicrat rib on your gun is top drawer, best Ron Powers built and he built the best. The four holes on the top of the rear sight were used for changing yardages. Preset ranges were sighted in then the appropiate hole on the top sight was punched. Usual yardage settings were: 7, 15, 25 and 50. As you moved from station to station a ball point pen was used to press the next appropiate button for sight picture/range.
Cannon moved to Montana over by Hamilton and worked a shop there. He did hire assistants, but the guns he built had the above features on the weapons. I stopped at his shop one time in the early 80s to drop off a 4" 624 and there was a brand new Redhawk with a 5.5" barrel that he had just rechambered to 45 Colt for Hank Williams Jr. who lived close by.
Great 686 shoot the snot out of it.