Stan,
Since case colors are the product of a reaction between steel, carbon, and heat, and no two lots of steel, bone or charcoal would be absolutely identical, nor would two quench solutions be absolutely identical, how can we assume wear rates or susceptibility to fade would be identical between different guns from different manufactures at different periods of time?

I read an article that made the point that Baker case colors were considered very durable in the era they were produced.

I have often wondered who came up with that, and how?

Best,
Ted