In addition to the other questions asked, if I may ask a few (possibly odd ones) as well, please? I’m just trying to think of other ways of looking for him.
After reading some of the comments, it appears that “Stan” had been in the Navy “awhile”. However, there’s no chance that he might still be living is there? I have an ancestor who was 105 when she passed and I know of two people who were about 97 years old when they passed, so I’m overly concerned about unlikely possibilities.
Were any small details shared either verbally or in the letters that could offer clues? Did he mention likes or dislikes such as: snow skiing, sailing, visiting historical and/or cultural North American places, certain foods (French Canadian, etc.), small or large town living, severe weather events, etc. Was his accent ever mentioned? Of course his family could have moved around Canada but residents in some parts of Canada have distinct accents. With luck, any little clues could point to different Canadian provinces. It was most likely not brought up, but do you know if any names were discussed for naming your mum the baby?
Could he have been around the same age as your grandmother? If she was rather young when she met him, possibly he was as well? If she was in her mid- to late-20s, perhaps he was as well?
Odd questions I know, but with little to go on so far, I thought that I would ask. I hope it isn’t too personal. Thank you, Lisa