Nestler 21a Darmstadt 58cm 23″ long slide rule 1950 Germany

This is a beautiful large slide rule using the Darmstadt system with number 21a. Due to the length it is more accurate than the standard model 21. I am guesstimating this one is from ca. 1950 since there are no screws. Everything is complete, no cracks, chips or dings and in working condition and very large glass cursor with 1 large and 2 small hairlines.  There are some signs of normal use and hardly any signs of age. The cursor is in close to new condition as well and has 2 sides, on the 3rd side there is a small pointer. Overall in a great condition. There are marks from storage on the corners and some staining on the original signed cardboard container, it is also signed on top but this is a bit harder to make out. It measures about 58 cm or 23 inches wide. Check the attached video on how to work your vintage man tool : slide rule operation instructions!