The removal of the names and division numbers was to avoid US intelligence gaining knowledge about the activities and organisation of Combined Fleet's units. In the war off China, there was no need to hide them, since the Chinese Fleet was at the bottom of the sea by 1937.
American hull numbers are rather small in comparaison, maybe that's why they kept them ?
yyzBegonia, you'll find more digitally colored pictures on the artist's website:
http://blog.livedoor.jp/irootoko_jr/
An amazing artist. I love how he respects the original quality of the photograph.
Also, I'd like to apologize to you for my last post. I seemed pretty rude, and my post was ignoring the info you gave on the names.