One of the pieces of feedback the German military got from the invasion of Poland in 1939 was a desire for a squad-level designated marksman in each unit. This would be a man with the best shooting skills of the unit, but not actually a fully trained sniper, and he should be equipped with a light and simple optical sight, for shooting at small targets like pillbox ports or sandbagged machine gun nests. To fill this need, development of what would become the ZF-40 and ZF-41 scope was started. It was initially envisioned as mounting to the G41(M) and G41(W) rifles, although this never actually happened.

Instead, by the time the scopes were ready for use, those fully-trained snipers were deemed a higher priority, and there were insufficient regulations ZF-39 type scopes in production to equip all the snipers being put through sniper school. So, the K98k with ZF-41 was used as a substitute sniper's rifle - much to the chagrin of those new snipers who found its 1.5x magnification and very narrow field of view sub-par. It would not be until the summer of 1944 that the K98k-ZF41 was finally classified as a rifle suitable for anyone in the infantry. Production would continue right to the end of the war, with over 100,000 of these optics being made. They are today the most common German scopes (and scoped rifles) of World War Two, and reproductions have also been made. Today we are looking at an original example with its scope case, as well as a reproduction to distinguish between them.

Ken Tomonari's very detailed web site on the ZF40/ZF41:
http://zielfernrohr.b.la9.jp/index.htm