Others here can identity the material for certain.

If you have the original shop invoice, that would also lock it down.

We like to have them stay pristine, but stuff happens.

No matter how we store non-stainless for example, no matter what preservative we use, they can get blemishes.

I have even had 440C get freckles when stored in a leather sheath.

The shop could probably stay pretty busy cleaning up knives, and do a good job of it, but sometimes it is not worth having it done.

Maybe somebody on here knows how you could clean up the discoloration?

Larry