Hi John, Just found your sextant on the dealerwebsite, he also sold a nice barograph, also yours now? About the numbers on the KM sextants. The number on the arc is the Plath factory serial number. The number with the Kriegsmarine eagle above M is the German Navy satisfactory stamp, or Kriegsmarine abnahme. So this meaned the navy approved the sextant, this was done on every Kriegsmarine item from field gear to navigational item.The department that did this for navigational items and clocks was the Deutsche Seewarte. This is also shown on the certificate in the box and probably on the left side of the arc " DS' is stamped. About the Kriegsmarine abnahme numbers; they put them on a lot of german equipment, sextants, clocks, binoculars, barographs, anemometers, barometers etc. They numbered them whatever came up first, that's my guess/ Floris