By 1980 production, you had better look hard at that best. There are era's for everything, and that was a bleak period for most English gunmaker's.
I wouldn't sell anything I shot really, really well-been there, done that. Don't sell grandpa's gun. Give further consideration to what loads and games you will be shooting in the future-a 20 bore Royal will suck if you are forced to use steel for hunting.
Adrift in this world of double guns, several things I've mostly learned. An English sidelock best is a delicate piece of machinery. They are not typically as reliable as a good pump. That doesn't mean I haven't loved various copies I've owned, nor will it prevent me from lusting after, or owning more good sidelock doubles. You will end up beholden to a good gunsmith. Good gunsmith's like steak and shrimp as much as anyone else.
Temper your desire's with the above, and see if the gun remains in the cards. Enjoy using it, if it does. If you are not enjoying it, find one you do.
Best,
Ted
