"The case, as mentioned, is very thin and contributes little, if anything useful, to deflection strength."
I do not agree with that statement. It is inconceivable to me that all the pre-WWII makers would have bothered with the difficult and costly case hardening of their doubles if that were true. Especially during the depression years, when cutting overhead was paramount for companies to reduce costs and stay in business.
Shooting an annealed gun more than a few times is just asking for trouble. That being said, just because a gun has had its frame blued does not necessarily mean that it was annealed. It is probably far more likely that the case colors were brushed off and then it was blued. Rusting agents will work just fine on a hardened frame.
