The Zeiss Optics D36 is a step up in lens quality, and at over $100 it is expensive. However, what you get with this level of loupe is a distortion-free image without chromatic aberration over the entire field of view. This Zeiss Optics D36 aplanatic-achromatic double loupe provides the additional benefit of being a single compact folding pocket loupe that has separate 3x and 6x lenses, which then can combine to provide 9x magnification.
Most watchmakers spend the bulk of their day between 4-6x, and the variety of magnification options you get with this loupe allow you to adjust between lower powers for comfortable viewing for longer periods of time and at bit farther distances, and then move to 9x magnification for more limited periods of time.
The lens diameter is a large 22mm and comes with antireflective coating. The field of view is 32/52/127mm (9x/6x/3x). Optimally the lens is 10mm from the eye, and the watch is 25/35/80mm from the lens. The body of the loupe is a reinforced polymer shell, providing enhanced shock protection for the lenses if the loupe is dropped.
If desired, the Zeiss Optics aplanatic-achromatic pocket magnifier is also available as a single pocket magnifier with either 24 D (3x) or 40 D (6x). The D indicates dioptric power, which makes it possible to determine the respective magnification depending on the continues of use. This loupe is a 36 D = 24 D + 12 D, indicating 9x = 6x + 3x.