It wasn’t just the lean years, W W Greener were building Anson and Deeley guns (under licence) before they developed the Facile Princeps to get round the royalty payments. They continued to build A&D side by side with the FP throughout their production history.
This A&D was a 30 Guinea non-ejector from 1878 and must have been one of their earliest A&D guns.
Thanks for the additional photos of the action. Your very nice gun is clearly built on an Empire action as it does not have the pronounced cocking dogs of the A&D.
If Remington were then loading 2 3/4” 10 bore it could well have been built for an American customer.