There are several listings for Hammond in British Directories, they are as follows:
Hammond Joseph, Gun and pistol maker, 39 1/2 Lower Loveday Street,Birmingham.
Hammond Isaac, Winchester Hampshire,[Or Hants] 1829--1867
Hammond Bros; 40 Jewry [or Jewry] Street Winchester Hampshire, Circa,1900.and at later dates.
The Winchester Hammond was most likely the retailer of the gun that you are interested in. In all probability the gun was made for them in Birmingham.

Roy Hebbes