Battery D 53rd A.A. Training Battalion

Someone posted this WWII photo in my local Buy Nothing Facebook group because they wanted to get rid of it. I naturally "rescued" it as I would hate to see something like this ever thrown away. It's in great shape considering it's been rolled tightly for so long.

This is Battery D 53rd A.A. Training Battalion at Camp Callan, California. This was taken on April 18, 1942. I'll need to do some research and see if I can find more info about this battalion. I'm sure some descendant would love to have this.

I'm not immediately seeing information online about this battalion, but do find info about Camp Callan. It was near San Diego and was an anti-aircraft artillery replacement training center and was operational only during WWII.