Updated: Jun 23
With thanks to the private collection that allowed me to view, research and document this rifle and magazine (the magazine features in other blogs also: Parker Hale accessories and a history of Lee Enfield magazines).
This specimen started as a BSA No1Mk3 in 1915, which represent some of the last of this model - which was then simplifies to the No1mk3*. So this retains the two piece volley sights (the front disk has the pointer and screw missing) and it would have had a windage adjustable rear sight but this was removed for the Canadian 1910 sight to see freely. It also retains the piling swivel on the nose cap. Later it was selected to become a .22 trainer version of the No1 rifle and has entered service with both Canada and South Africa.
The Canadian service added the 1910 model rear sight that was used on their .22 rifles. The bolt head shows a "U" stamp for union of South Africa in the British Commonwealth - this may have been a good used part from another rifle or original to the rifle all along. However the bolt has been converted to .22 rimfire configuration but not further modified for use with the Parker Hiscock magazine - which may have been added post service / in private ownership. The rifle also retains its butt disk indicating its Canadian service posting. This is also flanked by two broad arrow in a "C" Canadian service marks.