This is a rotating combination lock. The password can be changed by editing the piston memory tapes located inside the lock. The current password is 0000.

To change the code, first change the numbers to the code you want to have, then go into the machine to the 4 piston tapes (or more/less depending on whether you change the amount) with 9 pieces of glass and 1 normal block. Remove the 1 normal block in the tape and replace it with glass, then place the 1 block in the position shown in the 3rd picture. The 3rd picture shows what a correct number looks like, and the 4th shows what an incorrect number looks like (the 1 block can be in any position other than that shown in the 3rd picture).