Adam,

The following is from the Internet Gun Club website about George Smith:

George Smith started at 40 Davies Street in 1859. In 1866 he moved to 16 Davies Street and in 1867 to 104 New Bond Street. In 1869 he moved to 82 New Bond Street, but in 1870 he moved back to 10 Davies Street. In 1871 he moved to 253 Oxford Street, and in 1874 he was recorded at 3 Park Lane. In 1885 he was at 110 Mount Street and in 1888 at 3 Angel Court, King Street. In 1891 he was at 4 Stafford Street and in 1896 at 13 King Street. In 1897 the name of the firm was changed to George Smith & Co, and they finally managed to reach 153 Piccadilly which was probably their original goal! They closed after 12 months or so in 1897. No other gun maker in the whole of the UK occupied so many premises, 12 in less than 40 years.

Looks like he was on Davies Street from 1867 to 1869 and again between 1870 to 1871. I suspect the rifle would date to these years. Hope this helps.

John