I am not a collector...I just get given things. The time I was given the rifle I did not appreciate that you leave things as they are.
If you saw the daggers, knives and bayonets on display in my office (I don't collect edged weapons either) you would understand why people have a tendancy to give you items to add to the 'collection'. That started off with me having my one khukri on display that I had been given when we pulled out of Hong Kong.
All the best
Doug ; As a collector sanded/polished has virtually no different effect. They change the original finish and dull original markings. A s a collector whom centers on WW1 era rifles it can kill collector value significantly !. Plus the beauty of aged wood with the "patina" only time can bestow upon it is simply gorgeous. I've known bubbas that rub stocks down with acetone and even mean green detergent type soaps...ruins it to a collector !
You would have just loved the unopened box of K98s that I found in Berlin then!
I ended up giving them to the Schutzpolizei who sold them off down in West Germany
The two triggered Bruno LMG I did have restored at the local army workshop before it went on display in my office was another Berlin find.
As you may have gathered I am not a collector of weapons and being of the ilk I am a gun should be clean and ready for use...but I do appreciate what you say about keeping the original patina but this rifle really was in a sorry state when it turned up.
Happy collecting all the best