USN hull code for armored carriers, which all of these are.
Nah, CVB is still Aircraft Carrier, Large. You can see this pretty easily when you look at ONI's Royal Navy related documents and what USN-styled hull codes they issued to British ships. Illustrious-class (including Indominable) are listed as CV7 through CV10 in ONI 201 (United Kingdom Naval Vessels), and ONI 201-1 (Index to Warships of the British Commonwealth) lists Aircraft Carrier, Large as "No British Equivalent". The same documents also confirm that battlecruisers and large cruisers were different things as far as ONI was concerned, as battlecruisers got "No U.S. units" and large cruisers got "No British Equivalent". In general, those are pretty interesting documents, even if they have some pretty weird choices on occasion, like RN BB1-5 being R-class instead of the QEs that came before them or how in Germany related documents Hippers got lower hull numbers than Deutchlands (ONI 204 lists Hippers as CA1-5 and Deutchlands as CA6-8)
