I'll be darned. Good answer. I wonder if there was a time when PSA classified Canadian exhibits like they were no different than "American" ones or is it a mistake by PSA? Goes to your original point -- it gets complicated down in this rabbit hole! I do have Exhibitman's book, but it is at a different location.
It turns out I have three others, all with the diamond surrounding a card number. But a quick eBay search turns up 10 ungraded cards presented as 1953 Canadian Exhibits and all of them have card numbers, but without diamonds. No graded cards turn up.
https://www.net54baseball.com/attach...1&d=1658947751
https://www.net54baseball.com/attach...1&d=1658948098
https://www.net54baseball.com/attach...1&d=1658948209