A few years either way of the turn of the century
No
Smithsonian was the trade brand name used by Crescent Fire Arms Co. and later Crescent-Davis. The distributor/retailer was H & D Folsom. Likely production in the 1900-1925 time period. No relation to the Smithsonian Institute.
no homer Simpson did
YES
The current Barrett Firearms does not make a double shotgun. Exactly how is your gun marked?
The front trigger opened the breach.
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.
Impossible to answer. It HAS other markings on it somewhere.
Impossible to answer with information given. No make, no model, no condition?
Most likely Stevens they did make a model #5100
You must call Browning to find out.