Antique San Jose California made leather holster, by F M STERN. He made leather goods, including saddles. Harnesses and holsters in San Jose California from the 1850s on. This holster measures 9 inches by 5 1/4 inches.
F M STERN SADDLERY, established in 1852 in San Jose, is one of the oldest and most respected in California. Stern employed or represented some of the most accomplished bit and spur makers in California including Mardueno, Flores, Echavarria, and Larios, and carried a full-line of finely braided rawhide in addition to his renowned saddles. Information from an expert holstorian: Yes, when a maker has been in business so long it is wise to determine which era, and in that search, one can rely on sewing. But yours is laced as a maker would do if he didn't have a harness machine VERY expensive until early in the 20th century. Yours appears to have signs of red rot, which could be good news because this existed only in the mid 19th century and was eradicated by 1900.
I have no other examples of a Stern so I'd expect it to be as old as I said while pointing out that the olive pattern, which this is, first appeared in the 1870s, after the Civil War, for civilians who prior didn't carry handguns. C/b for either SA or DA revolvers, you'll want to check both while looking for alignment with black marks of the cylinder inside the holster pocket.