I think the true "bone and charcoal case hardening process" at the Huglu factory was an option for Dehaan and Kimber guns. I don't know if they all had it but know some did. Ordering a Dehaan was to some extent Au LaCarte menu on some features. Here is a Kimber that has it. I do know that even some of the CZ's had a hardening process that had a result of imitating the bone and charcoal look, but it wasn't the actual process.
https://www.gunsinternational.com/gu...n_id=101075729
Remember years ago RGS got a bunch of the Kimbers to auction off at banquets to generate some cash but had trouble getting rid of them. I think if you wanted a true sidelock that was made in last 15 years that would not break the bank and you got a lot of gun for the money, it would be hard not to look at em.