minute flaps is 60 the number of the hour flaps is selected to be 48 so as to make the number of the hour flaps to approach the number of the minute flaps and the hour flaps are actuated every 30 minutes so that the successive two pairs of the hour flaps indicate the same hour indication during every 30 minutes the operation of the device of the present invention shown in fig2 7 is as follows as shown in fig2 and 3 when the indication of the minute flaps approaches 45 minute the synchronizing member s slides along the inclined edge ca of the cam member c in contact therewith and rides on the land cb thereof so that the bent portion sb of the synchronizing member s moves into the path of movement of the hour flap now arrested by the holding member kt for arresting the same even though the holding member kt is disengaged from the hour flap thereafter as shown in fig4 and 5 when the indication of the minute flaps reaches 59 minutes the lug m59 39 of the hour flap m59 comes in contact with the portion sa of the synchronizing member s so as to actuate the same the land cb of the cam member c is.