The Zeiss 2.5x Glasvizier 16 optic is one of the most unusual and interesting of the German sighting systems used on rifles during the First World War. It is a bifocal optic, working in the same way as today’s SeeAll optic. Basically, a section of magnifying lens sits in the bottom third of the field of view, which magnifies the huge white triangle that clips over the rifle’s front sight. By lining the tip of this triangle up on your target, you can get a parallax-free sight picture. The front and rear portions are both clip-on and can be removed in seconds, allowing the system to be fielded without needing to permanently convert rifles to a sniper configuration. The system is interesting and does work, but like its SeeAll descendent today, it is not really what someone expects to get from a 2.5s optical sight. I don’t have any data on the number produced or the extent to which they were fielded during the war (although this particular optic is serialized #4807), but I suspect that its unorthodox nature led to a poor reputation amongst troops and a fairly limited field use. Certainly these are one of the rarest f the German WW1 optics, and one would expect to see more surviving if they had been widely used.