Spiritcrow
I don't think that the gentleman actually went to St Malo on a ship called the Foudroyant, I think that you will find that he crossed the Atlantic on a ship of the Royal Canadian Navy with a different name. You will know which one once you have received his service record from the BAC-LAC.
en.wikipedia.org
The scan from Lloyd's Register which I included in my earlier post shows that there was a trawler called Foudroyant registered in St Malo at exactly the right time. The script on the ring, by the way, is in a style which would fit with French script of the time. I note, too, that there is nothing like 'HMCS' on the ring; it seems quite clear that this isn't a ring from a military ship.
I think that your photo isn't of a matelot being photographed on his own ship, by the way; I think that it's a photo of a matelot larking about in the harbour near where his own ship is moored. There will have been a point, incidentally, as the War came to an end, when ships of the RCN were coming in to ports like St Malo to pick up troops and equipment returning to Canada.
I would suggest that what you have here is a kind of 'Selfie', one which says 'Greetings from France'. I think that he could have had a photo taken of himself wandering around with nothing showing the name of the place in question and no way of remembering in later years exactly where he was at the time. By grabbing this ring from an unattended trawler as he was bimbling along and framing his face with it, he was able to have a photo taken which he could look at once his film was developed and again as the years receded and know straightaway where he was when it was taken.
