Quick question: Case tru sharp blade has stainless backspring?

[the kid]

I noticed what I think is rust on the inside of the handle (on the back spring) of my stainless Case Sodbuster.
Black grey spots which don't go away when probing with a toothpick and WD-40.
I never had a pocket knife rust on me before so I'm a bit surprised.

So my question is:
Is the back spring also stainless steel on a tru sharp Case?

If yes, do the Case knives with carbon blades also come with stainless back springs?
(I might try a non stainless knife blade in the future, never had one before)

 

[Woodrow F Call]

I believe all modern Case back springs are are stainless. Stainless (at least certain forms) can rust if not taken care of, backsprings are more likely on the inside as they aren't as polished. Stainless is more resistant, but maybe not rust proof.