When Matt tells Burke that he want to move the payroll from his safe to the bank, Burke goes and unlocks the safe, and there is a counter blocking it so that no one would be able to see the combination being dialed. But earlier, when Ben was outside and he glanced in the window, there was nothing obstructing his view of the safe.
Ben reads the letter in the freight office safe. It says the payroll is coming to Dodge, then going to Garden City. But when he tells Barker and Hargis about it while planning the robbery, he says Hays City, instead of Garden City.
When Newly locks the bank door, he gives it a couple tugs to make sure it is locked, but the door is so flimsy, it wouldn't take much of a push from outside to open it.