Hello , I recently picked up these nice old pair of Zeiss Telac. So far I believe they are 1913 dated due to the serial number being 235739. I do have quite a few military binos in my collection and from my research I think they are civilian due to the small adjustment knob, the larger one bring military?. They have been engraved as per photos, one side being 1914 1919 the other is a symbol, then PT with 'frow' or something similar on it, both engravings do look period. My conclusion are that these are a civilian pair pressed into service in the military of some description....I stand to be corrected and any alternative information would be great , cheers .