I'm pretty sure the case hardening is real. The Heritage Model 10's were done by Turnbull and they had a clear coating to make them really shine and last. But I remember hearing that the coating on those Heritage models was just for show and it would come off with most gun cleaning fluids. Just the coating though, not the case hardening. It will always look great unless the gun is used and carried for the next 100 years!

As much as I love my nickel Model 40-1, sometimes I wish I had the case hardened version! They're just gorgeous!

S&W Model 40 Centennial | Tactical Response Magazine