Disney artist Hank Porter frequently added symbols to his designs to indicate the unit's designation. And in the case of the USS Wasp, he even added seven waves to the design in homage to the prior USS Wasp CV-7. The studio received an edict from the government banning the use of any identifier in a design, but it seems Porter ignored that edict on many occasions. I would presume the C.O. of many units had the identifier on their particular design removed so they wouldn't get in trouble form the higher-ups, or, if captured, the design wouldn't give away info to the enemy.
I cover this topic in the insignia chapter of my book: Service With Character. The Disney Studio and World War II. The book is available on Amazon in print and e-book formats. The e-book has images, the print version does not as Disney would not grant me permission to use the photos in the print version.