I only own (and tried) the Arsat 20 so I can’t compare it with the Nikkor-version. My experience with the Arsat on a Nikon FE2 and EM: the Arsat is fairly good – ie: it does the job. There is some fall-off in light and sharpness towards the edges, but that’s quite normal. At f2.8 the Arsat 20 is fairly unusable though: lights and white surfaces become radiant in the pictures, but at f4 the performance gets better and at f8 the lens is at its best. The construction is sturdy and all metal – I bought mine on eBay from Kievcamera for 100 $, but I don’t think it was checked before shipping: the mount was badly assembled and the lens didn’t mount completely – I got a new sets of screws from Kievcamera to replace the original ones, and those worked. “Made in the Ukraïne”, so buy at your own risk. My serial number btw is 200-something, I’m not sure this low serial number is an indication of the production numbers…