Ruger M77 Mark II Stainless .270 Win

This is a Ruger M77 Mark II .270 win in stainless with the synthetic stock. Ruger stainless scope rings and a Redfield 3X9 (not worth anything really but it comes with the rifle. The rifle has been used for target practice and deer hunting in NC. The only issue is the stock, there are many discolored spots that I tried to clean but had no luck getting out. I don't know what caused this, I'm selling the rifle for a good friend of mine whose husband passed away earlier this year. Any questions please don't hesitate to ask. Thank you. Glenn