The 19 mm Nikkor comes in RMS microscope screw mount and you will need an adapters to convert RMS to Leica thread and then to Nikon mount. The 19 mm f/2.8 Macro-Nikkor has working optimum at 20x and should be used indoor only, as the focusing distance is about 20mm. It is designed to be mounted on a bellow, and it’s range is from 15x to 40x at the maximum extension.
Macro-Nikkors are hard to find today and really expensive (my gem cost me over 1500 €). This lens was made in Japan almost 40 years ago. I usually mount this on a PB-6 with PB 6E, sometimes with PK rings too!
A devil bacio pare na onu Sigmu