I am unaware of any Hussey guns simply marked up as 'H Hussey, London'. There were two Hussey's, father and son; HJ & HH. They almost always made a point of signing their guns and barrels.
Unusually there are no tear drops on the stock, where there should be. The gun may have been restocked. However, I am a wee bit suspicious about this one.
What is the serial number on this gun, please? I have a register of guns made by both Hussey's, garnered over many years, though not complete, I hasten to add. However, it does allow me to date and identify guns under their names to a pretty good extent.
Tim