A Micro-Nikkor-PC: http://www.destoutz.ch/lens_55mm_f3.5_734997.html
A 55/3.5 Micro-Nikkor K version: http://www.destoutz.ch/lens_55mm_f3.5_910139.html
The compensating diaphragm 55/3.5's have a metal focusing ring usually marked with a distance scale in either meters or feet. Serial numbers are much lower, too, being below 300,000. As the helicoid is extended, the diaphragm slowly opens up.