Would first like to take the opportunity to Welcome you to TFL.
I don't know about your shotgun but I will say you have gotten some very good advice thus far as to NOT altering or messing with it or having anyone do anything to it till you find out what you have.
What some people deem as doing something minor to a collectible gun can turn a very high $ gun into a low end gun costing themselves several thousand $'s.
Again, you've already rec'v some good advice and there are some very knowledgeable people here on TFL when it comes to high-end collector shotguns. I'm sure you will hear from more of them.
Congratulations on your inheritance.