Savages,
The bomb with all the writing was Fat Man, but not the "...U.S.S. Indianapolis" inscription you mentioned. That particular inscription was on a model of Little Boy, not on the bomb itself. Here are a couple photos of Little Boy while it was being loaded into Enola Gay on Tinian.


**Note: These photos have long since been declassified, but the website (alternatewars.com) had the images cropped, cutting off the declass verbiage