There are no serial number records of these old Crescent shotguns. There are only guesses base on the style and features of the gun. Out side hammers were popular prior to and during WWI. and armory or fluid steel ( I read somewhere ) became popular about the same time, perhaps because of the lack of Belgium Damascus barrels and steel making process had improved so much.. So I would guess your shotgun was made approximately between 1900's and 1920. Just a guess.
And I have been wrong a few times before and will be again.