Questions on the "Classic Series" Models 40 & 42

[Nick Danger]

I recently picked up a set (3) of these neat little guns, and wondered about the durability of the finish on one in particular, the color case-hardened model 40. Anyone have experience with these 2 models, if so what do you think of them? The Model 42 is all black, aluminum frame, & I do believe that my model has a mim barrel. The underside of the barrel has an indentation point that looks as if the barrel came from a mold. The other 2 , Model 40s have forged steel barrels with a "J" stamped on the underside of the barrels. Any information on care of color case finish and if anyone knows whether S&W are using mim barrels on some models would be appreciated. Thanks.