Excact time chronometer watch used by watchmakers. Often these watches were displayed in the shop window to help the public adjust their pocket- and wristwatches. This high quality “deckwatch style” Zenith watch is set by stopping the balance wheel with the help of the steel rod you can see in the mahogany box. The power reserve indicator serves to remind the operator to wind the watch at the same time every 24 hours. This is the same procedure as the ship navigators had winding the marine chronometer at sea. Ca 1920.