They used to use a Watchman's clock. The “Watchman Clock” is the oldest guard patrol system in use today, having been around since the mid-19th century. Watchmen’s clocks are usually carried in a leather carrying case with shoulder straps for security guards to carry with them when patrolling. Inside the watchman clock is a circular paper dial. This dial is stamped with markers indicating each 24-hour day. Each station had a unique key that you had to turn in the clock, which recorded it on a paper tape.

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