Skinny, that barrel marking is the most common for the 1849 pocket pistol, being used from c. 187000 to end of production at c. 340000. The Model 1849 had, IIRC, the highest production of any Colt percussion revolver and the basic frame was used for the 1862 Police, the Pocket Navy, and some conversions as well as cartridge revolvers, the latter being made as late as 1880.
One result of the numbers made and the variations is that it is also has aroused a lot of controversy over various esoteric details, with collectors firing books and magazine articles at one another for years. (So far there have been no fatalities, but a number of theories have been blown up by the research.) Much of the dispute arises over the relation of the Pocket pistol to the Baby Dragoon; most purists seem to forget that Sam Colt never threw anything away and that if old surplus parts were usable in a new model, they were used.
Those guns all had silver plated grip straps, but the plating was thin* and it is uncommon to find one with that much plating intact. Please don't do anything to the finish.
* It was called "silver wash" at the time, although it was one of the first uses of the then-new electroplating.
Jim