[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.

Jim