Trust is a good thing, but how can the management know whether the night guard has conducted the night watch as scheduled? Special control clocks have been in existence as from the 19th century. With a key placed at each location to be controlled, the location and time of the guard’s whereabouts were documented on a strip of paper inside the clock. Control is simply best.
To ascertain that false keys could not be used, in 1878 Eduard Eppner of Breslau developed “a safety mechanism to guard against the use of unauthorised keys”.
Yet, what if the night guard had changed the time? Although only one key could open this clock, locks can be picked. Eduard Eppner found a solution for this problem as well: his patent also included “a mechanism whereby the premature opening of the case is marked”.
And, what of it ... ? In the end, nothing is better than trust.
Watchclock with Case and Key, A. Eppner & Co., Breslau, c. 1900, Inv. 2017-011