I went back and checked my guns. I erred on my ID. Your action is the Henry action, not the Whitney one. I have changed the info below.At the end of the civil war, manufacturers had a large surplus of musket barrels in inventory. They bored them smooth and attached them to a proprietary boxlock action of their design. The result was an inexpensive shotgun that could be marketed. These are often mis-identified as Wesson actions, but they aren't.
That particular action is a Henry as identified by the screw on sideplate that covered the internals. I have 2 of them. They were made from 1866-1869. I have no further info on this model.
Whitney made a similar action but the sideplate screwed into the action and Remington had one with a center hung hammer (Remington's 1st inline)
As an aside, the internal configuration of Pete Allen's boxlock closely resembles the internals of an Iver Johnson Arms and Cycle Works Champion shotgun made around the turn of the 20th century. I also have one of those and it was $16 when new.
Top to bottom: Henry, Whitney, Remington
