Hello all, I am working on refinishing an old Remington 870 gun stock. It is a vintage police department take off set and is solid walnut.

I will be finishing with Sam Maloof poly oil for a satin finish. I have already started on the stock itself and it looks great!

I stripped down the forend and cannot seem to get rid of these "black spots" - not even sure what it is! Old stain? Residue from the gun being fired?

I tried sanding over it, but doesn't even seem take anything off. Any ideas?

Here's what the stock set looked like when I got it. What an awful finish!
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Here are the black areas I am speaking of:
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