I would guess circa 1875-76 but i will find out by the serial numbers.
These were made by the Abingdon Gun works of Birmingham, who later went on to produce Motor cycles, only ceasing business 10 years or so ago, called Abingdon King Dick, making tools and spanners. In the 1870's- they were listed as gun makers and Vice (for tool benches) manufacturers.
This example was made for V R Blakemore. chambering the .450/577 Martini round.
They also made Swinburn Rifles, In Zulu, when Hitch proclaims, how can I shoot them If I can't see them! he has a Swinburn rifle, he cocks it with the long thumblever.