The keys can now be removed, as they are not longer required. Now take a closer look at the hidden slider. It shows a puzzle piece and 2 symbols in it. The same symbols can be found on the cryptographic gearwheels.

The blue arrow in the photo shows the order in which the symbols on the gears should be set. The red arrow points to the first puzzle piece in the chain, which looks like a torn-off sheet of paper. Its edge fits the edge of the puzzle piece on the slider.

This suggests that those 2 symbols on the slider must be set on the 1st and 2nd gearwheels.

The other edge of the puzzle piece on the slider fits the one on the bottom surface of the box. Now you know the third symbol to be set on the gear.

Look for the other puzzle pieces and follow this principle until the symbols on the gearwheels are set in the correct order.

Now you can take out the lock from the side.