marketing ploy
Yes. Ruger has sn data on their website.
1977
Ruger red Label over and under 20 guage in very good condition, what is it worth 300-475 USD
Goo Gone or Goof Off will both do this easily.
600 or so
100-1000 depending on specifics
400-700
Yes, Target has a few label makers available at their store. They carry pretty standard options and good name brands.
Can't be answered without a DETAILED description of ALL markings, to include label on box.
You need to seek the services of a qualified appraiser.
100-1000 USD depending on specifics
Try Goof Off or Goo Gone. Available at home improving stores.