I have a Rod Cocking, Side Pivot top lever Lefever, so built around 1890 which has 3" chambers. This is a 32" 10 lb gun.
I have a 12 gauge W Richards with Birmingham black powder proofs which has a similar rib marking to yours, don't recall off hand exactly. It has been suggested this one was likely built by J P Clabrough. The proof marks will tell its origin of birth, but it is not connected with Westley Richards.
"Most" early American built tens will be found with 2 5/8 or 2 7/8 chambers but other lengths were available on order.
