As with all other types of firearms in the United States, shotguns must be engraved with a serial number by the manufacturer. This serial number often provides information about the date and place of manufacture.
The Gun Control Act of 1968 stipulates that all firearms must bear a serial number from the manufacturer, and that this serial number cannot be obscured or removed. Serial number locations will vary between models and manufacturers, but the numbers are frequently found on the bottom of the butt or on the inside of the frame. Manufacturers sometimes allow owners to look up the date of a gun's manufacture by entering the serial number into a website tool.