A real gem

I recently bought a used Nikon AFD 35/70 constant aperture short zoom for not a lot of money. By that I mean £65 in UK. OK the condition is not quite 'mint' but is isn't that bad, although there was a fair bit of dust inside. I had it cleaned and put back together and took it for a test. It is a heavy lens, of that you can have no doubt but the QUALITY of the images is outstanding! I don't think I have ever used a sharper zoom lens. There is virtually no distortion, either barrel or pincushion. A 12x16 colour print from my darkroom shows no fall off even in the extreme corners (F8-11 taking aperture).

Have I accidentally bought a 'good-un' or were they all like this?