@zuke... yes it is Canadian... Three Rivers, Quebec ( the plant was/is actually across the river at Cap de la Madellaine, QC... the old Dominion Rubber factory)
Also, would have to say that it's probably an Oerlikon round... my Mum used to make them, and the .5 Vickers there.
( If you still have it, pls email me... always interested in TR ammo...)