Silent Watchman Keys

I posted a bunch of old keys I found on the Finds Thread today. I was able to google and find pictures and info on most of them, but not these. I thought they were super cool. Does anyone know anything about them, what time period they would be and what they were used for? Thanks. I bought 4 of these, here is the view of the front/back.

 

Are you familiar with the Silent Watchmen system? Time clock stations were placed around a building and when the night watchman made his rounds he placed his key in each station as he came to it and turned it. There should be a raised number towards the end of the key and this imprinted the guard's number on a sheet of paper with time marked on it. The paper was driven by the clockworks.

This kept the watchman honest and showed he had made his rounds and at what time. If the keys do not have a raised number on the shank then they are used to open the box itself and retrieve the marked papers I guess. They don't really look like the watchman's keys as I remember them. They looked more like an old skeleton key.

I don't know when they started but this system was still in use in the 1990s and newer versions still are.

Dennis

 

No numbers on the keys. I am thinking maybe retrieval keys....since these are not common, I may have to go back and see if there are anymore. I know I left one there. Thank you for the information!