In doctoring up my tired old New Services I just file and fit to make hammers, triggers, etc. function. If they were ever hardened, case or otherwise I can't tell. Maybe the case (if any) was worn through before I got involved. They can be cut with a common file but seem to be about the hardness of a carbon steel spring.

I could case harden them with Kasenit but not knowing the carbon content of the part, if it is high carbon it would then be hardened all the way thru. So I leave them as-is when I get the function I want. If they are too soft and wear rapidly, I don't shoot enough for it likely to matter.

I don't recall doing it in any Colt work, but I have done weld built-up of critical worn parts, re-fit, then cased hardened, then drawn down to spring temper to relieve any brittleness.

I've had .44 S&W DA top breaks that wont stand full cock. It's about a 20 minute job to pull the hammer and sharpen the full-cock notch with a little diamond triangle file.

For those who don't know, Kasenit (there are others) is a powder product, you heat the part to red, dip it in or coat it good with the powder, keep it about 30 seconds at red heat coated with the product, then quench in water. It will then be glass hard. If you do this to high carbon steel, such as a knife blade, it will be glass hard all the way through and also be brittle like glass.