I'm still trying to figure out how the finish on a gun ends up like this one. Rust blue is supposed to be better than the newer types of bluing. Also my dad bought a Remington 1100 in 1964. Hunted the hell out of it at least several times a week during bird season, used it for ducks, used it as w back up trap gun. Then he gave it to me and I hunted it at least 3 times a week during quail and pheasant season, used it as my duck gun and my primary trap gun for about 20 years and the bluing still looks about new. What did people used to do with some of these poor guns to make the metal finish so bad.
Leaving them outdoors in a case where fabric touches metal will do that over time if you are anywhere very humid... eats the bluing right off.
I have an uncle in MN who always left rifles in a soft case in the trunks of his cars, and they pretty much all look like that, with little to no bluing, and pits. He cleans them just often enough to be functional about once a year, but other than that, they stay in the car all year.