Might just be a tightly barrelled 10 bore. Never seen a 12/10 combination. Does it chamber a ten bore cartridge freely in both barrels? Black powder proof gun. I can only find details of one Grove and that was a James in Birmingham but was later than the date of your gun. I have found a Robert Groves (different spelling) in Richmond, Yorkshire but he pre dates your gun. It will all rest on the condition of the barrels. Interesting gun and worth checking out for usability.
It seems that more of these old British 10 bores turn up in America than here back in Britain. I have a job finding them. Lagopus.....
