Below are examples of various style clocks National Cash Register produced as an extra with your cash register purchase. When an employee was left unattended to close the store, they had to stop the clock before they left for the night. The next day when the owner arrived to open shop, he would see what time the employee left the night before. This gave the owner a better since a security to leave the employee unsupervised.

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Top row from left: (Fine Scroll wide case hinged, Fine Scroll narrow case hinged)
Bottom row from left: (Empire with locking ring, Fine Scroll no hinge)
Far right: (Renaissance with Day/Night face)

This picture shows the difference in the wide case (left) and the narrow case (right) hinged clocks.
These are rare and very desirable to register collectors

(Picture of a wide cased hinged clock on a rare model 0)

(Picture of a solid white face clock on a fine scroll model 5)

(Picture of a solid white face clock on a renaissance case)

Right: (Front facing time stamp clock 500 class)
Left: (side facing time stamp clock 500 class)