In response to your observations re: AG photos.
With considerable time in the AG I did not see many shutterbugs on board. It is my recollection that cameras were frowned on if not actually forbidden
A couple of exceptions - after the war I received a series of photos taken by a Coast Guard sailor. I saw him taking the photos and asked that he send me a set which he did COD. They were taken in Leyte Gulf and Mindoro and with poor judgement I lent them to a AG and so long photos,.
My last ship carried some troops and the ship had a photographer and he too provide me with some taken in Manila.
A last exception was access to some film taken by the photographer on the USS Bush, an escort destroyer on a trip to Mindoro.
Over the years I have reflected on the photo opportunities missed.
So your acquired collection could be rare, if not uncommon.