I've not seen these guns (sub gauge) in the 5-6K range even well worn and tired
I recently acquired a 20 gauge Trap Skeet in beautifully admirable original condition (90%) and willingly gave 10K.
Winchester just didn't make that many.
Here's a 16 gauge Tournament skeet, again in beautiful admirable original condition.
Private party first vetted me and then agreed to take 8K.
These are scarce and beautiful guns, hell on a Skeet field and perfect upland Quail getters.
Looking at the degradation in the blue I would venture a guess that the metal finishes on your gun are original.
The wood should show equi imperfections to prove its' originality. Negative on the 2 9/16 chambers. 2 3/4 or 3" only.
How about more pictures please. Floor plate please and clear pictures of each side of the butt stock.
Have you got Cody info on this gun? I'd be interested to see if it began its' existance with a checkered butt.