To determine the exact value of a Pietro Berretta double barrel shotgun a number of factors would actually need to be taken into consideration. Most importantly, the condition of the shotgun.
Made between the early 1920s and 1940s by Stevens for Hibbard, Spencer, Bartlett and Co. $150-$250, depending on condition.
Franchi
A 12 gauge boxlock, double barrel shotgun with 30" barrels, double triggers, and extractors. Blued with a silve finished receiver and a checkered walnut stock. Discontinued in 1967. Exc VG Good Fair Poor 500 450 375 250 150 serial number c26613 excellent condition
Try gun shows, Shotgun News, Gun List, local gun shops.
Krupp is a German steel company. they made military guns during the wars Germany had. I believe krupp also made shotguns, but not sure
Assuming you mean the Silver II over/under shotgun imported by American Arms, they are selling in the $450 range in excellent condition. sales@countrygunsmith.net
can you find any information on a 410 gauge o/u by American arms inc. made in Italy? thank you
Royal Damascus was a mark used by Ancien Etablisment Pieper of Herstal, Belgium, c. 1890-1914. T Barker is usually dismissed as "just another Belgian clunker", but with a silver escution and engraving, yours is probably better than the average utility shotgun from the period. I have heard that T Barker was a hardware outlet in California, but have no proof of that.
That will depend on which Iver Johnson you have. The one most commonly encountered is the single shot Champion which will range from $25 for a parts gun to $150 in like-new condition. If it has a matted rib, add $25 in all grades. If it has a ventilated rib, those prices nearly double. Then there are the Skeeter Model and the Super Trap, both single shots which run from $375 to $1100. A Hercules Grade side by side double barrel lists from $250 to $550 and the Silver Shadow, an over-under double barrel manufactured in Italy for Iver Johnson, lists from $150 to $350.
If there are no other marks, it will be pretty difficult to identify the maker or exact age of your shotgun. I can say it was definitely made after the 1914 patent date, so it is considered a modern gun by collectors. I can also guarantee you that it was not used in any war. There haven't been any double barrel shotguns used by any army since the US Civil War, and only a few then. Unless it has fancy engraving, carving, or silver-plated parts, it's neither rare nor valuable, but as your grandfather's gun it should be priceless to you and your cousins. I have know nothing about J.N. Scott, but there is another thread on this page that has some information.
Sterling Silver Shotgun in DarkoviaForest