Lovely rifle! I don't know a lot about Canadianicon service markings but I recall a C with a broad arrow in it being consistent with Canadian issue.

It was made at the Royal Small Arms Factory Enfield (in the north of London) in 1917; during the reign of King George V - hence the Crown over GR (George Rex) stamping on the wristguard.

Looks like it's got a short length stock on it as well, judging from the "S" stamped on top of it near the buttplate and it's got the butt disc with it too - originally these had unit and regimental numbers stamped on them but this was discontinued in WWI.