Jeweler,
I believe this is Westley Richards Patent No.1572 of 1871.
This is not my collecting specialty but I own this model
and two other variations. With the introduction of centerfire cartridges in c.1867, a number of makers (including Westley Richards) offered dual ignition guns (center and pinfire). Your model, with pin slots in the barrels, could have been a dual ignition.
If you remove your firing pins you'll note that they're a bit of a 'rube goldberg' design that works via a 'wedging action.' When the top piece is struck by the hammer it forces the 'half-moon' shaped pin out of the breech face.
I think Steve has a good point. I cannot get to the picture trail portion of Monte's post, so cannot see if the Richards has slots in the barrel breech for pinfire pins, but the hammers are pinfire hammers, complete with the "rest" block that would bear on the top of the standing breech after firing. The hammers are sized so that they would strike the pin easily where it sits approx. .100" from the standing breech. I think if used as a pinfire, the dual ignition centerfire firing pins would be removed.
If the gun does not have the cutouts for the pinfire pins in the barrel, then the gun could be a conversion or even rebarreled . More pictures might help.
