Found this that I had saved in my files from several years back..... See what you all think >>>>>>>
What is Color Case Hardening?
Color case hardening (sometimes referred to as case-hardening, case color hardening, or surface hardening) is a heat treating process and one of the earliest ways of hardening lower-grade steel. Originally, this process used bone charcoal heated to an exact temperature. Afterwards, the parts were removed from the furnace and quenched. The process leaves a hard surface finish and a layer of colored carbon with beautiful color variations. While the process is very controlled and the results are predictable, the exact color combination and pattern is unique to each firearm.
This process is different from the potassium cyanide salt bath process, utilized by modern manufacturers in today's time. Colt actually had perfected the use of this original bone charcoal process many decades ago, and is still to this day known throughout the world as the original case hardening process that is second to none.