: Underneath the barrel or on the barrel flat near the chamber.
On the barrel or receiver, look for patent dates. These are your best clues for a because they provide a terminus post quem (the earliest possible year of manufacture).
Unlike modern guns, many 19th-century shotguns did not use a master serial number that correlates directly to a production year. Some had serial numbers only for inventory control; others had none at all. Many lower-cost models used assembly numbers (matching the barrel to the receiver) that hold no historical record.
Later “Bay State” shotguns (early 1900s) were actually made by Iver Johnson or H&R after they acquired the designs. A serial number lookup would require knowing which actual factory made the gun.
They purchased the Bay State Gun name around 1909 and continued production until approximately 1915 .
If your serial number falls into the Crescent range (25k-70k), then you can use the , which is better preserved. A lookup for a Crescent-made “Bay State” will show manufacture between 1892 and 1910.
To find the right lookup table, you must first determine who made your specific shotgun. The "Bay State" brand was used by three main entities: Harrington & Richardson (H&R):
: Often on the side or bottom of the frame.
