Ive been eyeing up a few LC Smiths for a possible purchase. I noticed on a lot of them the receiver has a certain type of corrosion. It looks different than the standard patina of an older gun. A little bit of case color left and the barrels and stock are in good condition but it has a weird patina to the receiver.

Does anyone know what Im talking about? Does anyone have an explanation? Does it affect the integrity of the metal?

Thanks!