My dear friend if an item is above 100 years selling that item is illegal. as per law if an item is above 100 years it is government property and you cannot sell that item , if you are caught selling the government will confesticate the item and go to court.. if he gets it registered he cannot sell it. But what abid said is right you need to at least know the history. As the sellers would be interested in buying only when you know what is it, the metal, the properties, the decade and other details.