Canadian Regimental markings help

[Guamsst]

Can anyone here give me a bit of help with the regimental marks on my P08 cavalry saber? It is British made, Canadian property stamped with the following marks on the basket
IO 5I
IO AD (possibly IS AD)
C over RS
IA MR (1st Alberta Mounted Rifles)

I have no idea what the first three sets of marks represent. The first I is most likely a roman numeral 1 for 1st.....
THANK YOU

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