How did Robert Newell’s Parautoptic lock make lock picking harder?

Robert Newell’s Parautoptic lock, produced by the firm of Day and Newell, enhanced security and thwarted lock picking through several innovative design features:

• Dual-Lever System: It utilized two sets of lever tumblers, with the first set acting upon the second, creating a more complex internal mechanism.1
• Inspection Prevention: It incorporated a plate that revolved with the key, which prevented unauthorized inspection of the lock's interior—a critical step in stopping lock pickers.1
• Interchangeable Key Bits: The lock featured a key with interchangeable bits, allowing the key configuration to be readily altered.1

Due to these sophisticated design elements, the Parautoptic lock was highly effective; despite numerous attempts to compromise it, there is no record of the device ever being successfully picked.1