The only thing I could find on the google machine is that the BB-242/U is an old Navy battery. The exact phrase was that it was a "Lantern, US Navy Ship Damage Control". Now what in the hell that means your guess is as good as mine. The battery looks like it's still in use it's just updated. They had a picture of a new one.
I have no idea. Most military batteries are item specific. There are certain batteries for radios, gps',.......and so on. It looks like someone before you had em wired in series powering something. Those things have gotta be over 20 years old.