While staying at the Witherup House in Franklin PA, I found :

It was published in 1946, when memories were fresh and ISBNs hadn’t yet been invented:

Paging through it, I found a photo similar to one I’d grown up with (clicky for more many dots):

None of those guys look like Dad.
Many of the events in World War II made little sense until the declassification of the Enigma decryptions and the ensuing Ultra / Magic programs showed the value of weaponized math …
I assume you’ve seen the writeup at https://www.asisbiz.com/Vanuatu/SS-President-Coolidge.html? I haven’t read it detail (very long) but looks fascinating.