$100 to $250, depending on the exact model and its condition.
Circa 1890-1930. Would have to have more information to get closer. firstname.lastname@example.org
THey were made by crescent firearm company.
Plymouth was a trade brand shotgun made by Crescent Fire Arms Co and later by Davis-Warner Arms Co. It was distributed/retailed by H & D Folsome. Shotgun Markings also lists a hammer double barrel by an unknown Belgian maker and indicates the retailer was Spear & Co.
It would be somewhere between 1893 and 1930.
The current Barrett Firearms does not make a double shotgun. Exactly how is your gun marked?
How much is a 16 gage single barrel shotgun model 350A Revelation