Combination lock with two dial plates

A combination lock comprising:

• a case unit having an outer case, an inner case and a cover, the outer case having a chamber and a passage which communicates with the chamber, the chamber having an open end, the inner case having a first chamber and a second chamber, a recess defined through a wall of the inner case, the cover connected to the open end and sealing the second chamber;
• a latch unit having a latch and a spring which is mounted to the latch, the latch movably inserted in the passage and having a first end thereof located in the chamber of the outer case, an end piece extending from the first end of the latch and movable in the recess of the inner case, the spring providing a force to move the latch in a direction away from the chamber of the outer case;
• a front unit having a tube and multiple disks which are mounted to the tube, a first end of the tube rotatably connected to the inner case and a second end of the tube rotatably extending through a closed end of the chamber, the disks driving each other and rotatable in the first chamber, each disk having a notch through which the end piece passes, one of the disks fixed to the tube and the rest of the disks rotatable relative to the tube;
• a first dial plate located on the outside of the closed end of the chamber of the outer case and fixed to the tube;
• a rear unit having a shaft and multiple disks which are mounted to the shaft, the shaft rotatably extending through the tube, a first end of the shaft extending into the second chamber and a second end of the shaft extending through the first dial plate, the disks driving each other and rotatable in the second chamber, each disk having a notch through which the end piece passes, one of the disks of the rear unit fixed to the shaft and the rest of the disks rotatable relative to the shaft, and
• a second dial plate located on the outside of the first dial plate and fixed to the shaft.