mfsob
kind of funny that Only in the Silent Service can you find a class of ships where every single one is unique.
That's common to all Naval vessels, really. Just more dramatic with subs as a general rule (and magnified by their smaller size.
As a "for instance" USN built 175 Fletcher Class DDs. No two are more than "generally" alike. Even the first 25 "round bridge" Fetchers were built in three different yards. So, they were similar, but not the same.
Shoot, three of them had the after torpedo mount and Mount 53 removed and a sruiser catapault installed to launch a single Kingfisher.
AA and ASW fit was unique to each hull, too.
Not just subs and DDs, either. The four Iowa battelships were laid down nearly at the same time, and still manage to not be identicial. Similar, especially at 500 or 1000 yards away, but with enough individual features to pick out the difference.
Just part of the process in Naval Ship Modeling.