The major advance in this model over I.D. 712 is the adoption of a dial with 48-hour rotation, giving coverage for two days.  The dial is divided into four 12-hour periods, marked DAY and NIGHT.  The clock is 14" square, versus the former 10," a change probably stemming from the desire to maintain good definition on a 48-hour dial.

This mechanism incorporates a plunger by which the watchman pricks the chart on his visit; a case lock; and a plunger by which the chart is pricked when the case lock is accessed by turning aside its cover.