I've spoken with some bubblehead Sonar techs who quite cheerfully claimed they could not only identify name/hull number/country of origin/date of launch and last refit, but tell you how many cups of coffee the galley had served and the color of the Captain's jockey shorts.
They may have been exaggerating about those jockey shorts, but not much else.
How does USN know which subs are NK?
“I’ve spoken with some bubblehead Sonar techs who quite cheerfully claimed they could not only identify name/hull number/country of origin/date of launch and last refit, but tell you how many cups of coffee the galley had served and the color of the Captain’s jockey shorts.
They may have been exaggerating about those jockey shorts, but not much else.”
Great answer. Since the Cold War, we have identified every submarine from moment of launch by friends, foes and in between.