This is a close-up view of the early analog to digital “punch” data recorders that replaced the earlier pen-and-ink strip recorders. These devices would literally punch a hole into a specially marked strip of paper every six minutes, recording the tidal level at that time. At regular intervals, the paper strips would be removed from the devices and fed into electronic computers. The punches from the strips would be analyzed and graphed. These devices were the precursers to today's advanced electronic monitoring systems. Although more accurate than the older pen-and-ink recorders, they still required frequent maintenance and adjustments.