Looks like 1928. The Blue Book says that 95% of the Parkers bought and sold each year have less than 30% original finish, so unless yours is one of the other 5%, it's worth $1800 according to that guide. If higher grades are that hard to find, I'd expect the price to skyrocket, but a 98% gun lists for just a bit more than twice as much. I think it was in the Standard Catalog that I saw the recommendation that anyone buying or selling a Parker Brothers should get a hands-on appraisal from a recognized expert.
Between $10 and $5,000. It will depend on the model and condition.
Since the Parker guns have been out of production for over 50 years, I would start with the Parker Collector's Association.
100-10000 depending on EXACTLY what you have.
I acquired a Mossberg 500 AG shotgun. It has never been fired and might be 10 years old. What is the value?
1886; 10-1000 USd
Value runs from $10 to $200 depending on condition