You are asking a question that has almost zero possiblity of being answered. You have not provided any information beyond the serial number. This is equivalent to walking into a car dealer and saying "I have car, what is it worth?". If you can provide the name of the maker (Belgium has many gun makers), caliber/gauge, type of action, type of weapon ( hand gun or long gun) and a detailed description of finish, features, wood used in the stock, accessories, any engraving and if origianal paper work is present, someone might be able to help.