If the gun is a family heirloom it is of course priceless...but it carries very little practical value.
Full factory original restoration (reblue and possibly hone the barrels, case color the action, refinish the stock, internal check and clean) will cost 10X the value of the gun, and "quick" is for the most part incompatible with "well done." And why remove the evidence of the joy afield the gun provided a family member?
Have you seen this thread? It has an estimated date of manufacture chart
https://www.shotgunworld.com/bbs/viewto ... 5&t=308333