Hi Dave and thank you for the welcome to the Site!
In regards to your questions:
First The gun was purchased during as you see it. I cannot tell you why the receiver has the color it does.
Second the odd things on the face of the breech are bugs! Yeah I know it needs a cleaning! Pretty funny stuff.
Third the patterns on the water table areas appear to be almost like an acid etched “pattern” I am guessing for decoration? Like adding a “jeweled” pattern to a bolt rifle bolt.
Yes I figure a value would be difficult to achieve. My father-in-law just wants to know if he has a $500 or a $5000 gun. Our next step may be just giving it a good cleaning after I bust a few clays with it then putting it away again.
Thank you so much for your input!