Mills,
The Maker/seller of your was most likely Henry Richards of,51 Oldhall Street,Liverpool,active 1858-1870. London records of the era do not show a gunmaker by the name Henry Richards active after 1811.
It is remotely possible that Henry was a London Ironmonger[Hardware store] who sold Birmingham made guns engraved with his name.
Many guns of provincial origin are found with the top rib engraved," London fine Twist" [or Damascus,] This was a marketing ploy used by some provincial gun makers to imply that the gun was at least in part London made and thus justified serious consideration by any prospective purchaser.
Recommend that you post pictures of your gun including the Proof marks,we will then be able to confirm origin.