As I understand it, the bank owner (Albert Case) told the robbers to steal the contents of that safety deposit box, as it contained evidence that he became rich doing business with the Nazis. If I'm right, and the guy owns the bank, why didn't he just walk in and empty the deposit box himself?!
Also, I don't fully understand the 'secret room' bit. Were the robbers drilling a pathway into the secret room behind the storage room? AND, when was the storage room built, because it seems that it was designed so that there was a 'secret room' behind it!