These 2cm telescopes are fairly common. They are mounted alongside the reflexsive/reflecting sight on the carriage of the flak gun. These telescopes are the sister models to the Zielfernrohr 3x8s used in the Pak 38, 40 and 41/43 anti-tank guns. These Flak Zielfernrohr, therefore, have the same optical properties and are meant to engage ground targets, not air. I dont like giving out prices because people who do that creates undue expectations and improper starting prices and ridiculous auction amounts, but in the amount of oxidation this one has suffered and the amount of mold on the ocular lens (cleanable), you shouldnt expect more than 200 e for it. Flak ZFs are not especially rare items, but......if you need one...you need one.