Originally Posted by Jim K
Another FWIW, color case hardening could be ordered on the 94 at extra cost, but was rare since the 94 was made with a steel receiver from the beginning, where the older rifles had receivers made from wrought iron. Iron can't be hardened, so the only way to get a wear-resistant surface was case hardening - the color was an option. The steel receivers could be hardened, so case hardening was no longer needed and was a costly and time-consuming process that sometimes ruined the receiver, so makers dropped it as soon as they could. A few makers (e.g., Colt) kept it for cosmetic purposes and as a kind of trademark, but it was no longer necessary.
Winchester shifted to steel receiver frames in the late 1870s, and they continued to color case harden the Models 1873, 1876, 1885, 1886, and 1887 right up to August of 1901. Color case hardening could be special ordered on the Models 1892 and 1894 up to that same date.