I have no rational idea but it's a pretty good looking cap. The center piece may be an aftermarket add on that was sold in Canada back when. Buy four of them at the Canadian version of Western Auto or Pep Boys and stick them on the hubcaps to dress them up. There might be part of an emblem under those if that is the case.
Look like 55 Mercury but I've never seen these on any Meteor Monarch so I'm inclined to agree with the aftermarket add on from Canadian Tire etc theory
The base cap looks like a '58 Imperial cover that I have hangin on the wall. Don't know about the additions to it. Is it 14"?
its a 15" cap, i have 2 of them....i found them in the trunk of a 50 studebaker champion 2 door sedan, i have seen a similar (but different size) maple leaf on the dash of a 53 studebaker(canadian built)
Sure looks like the '55 Merc caps I have on my '49, with the center star over top of it. Can you see the Mercury head from the back side? Maybe Canadian Merc is a pretty good bet if no head on it.