How did the revolving plate in the Parautoptic lock protect its interior from inspection?

The Parautoptic lock, developed by Robert Newell of the firm Day and Newell, protected its interior from inspection by incorporating a plate that revolved in tandem with the key. By rotating along with the key, this plate effectively blocked any view of the lock's internal mechanisms, which was a significant advancement in preventing lock picking.1

In addition to this revolving plate, the lock featured two sets of lever tumblers—with the first set operating the second—and utilized a key with interchangeable bits, allowing for easy alteration of the key's configuration. These combined security features were so effective that there is no record of the Parautoptic lock ever being successfully picked.1