Secret Safes

You walk into an underground casino. The room is dark, with wood panelling on the walls and a dimly lit chandelier overhead. There are a few paintings on the walls, and a locked safe to your left with a four-digit combination. In the center of the room, there's a card table with a few objects on top. You approach to take a closer look.

On the table, there are a few stacks of bills of different denominations. You soon notice, though, that one of the stacks seems fake: it's a bunch of $300 bills. You notice that the serial number has four digits! You run over to the safe to check.

The combo works! But the safe is empty... As it swings open, though, you hear a noise behind you.

It's one of the paintings! Slowly sliding over, the painting reveals another safe. This time, though, it's a three digit combination. You scan the room for more clues.

On the far wall, you spy a dart board with three darts stuck into it. You run over and note the number of points earned by each dart. Maybe this is a clue? You run back over to the safe to try it out.

It works! Inside the safe is a key, which opens the door on the far side of the room.