Funny thing is that when the F100 was released the big argument was that the metal lens mount was not of the same quality as the metal used for the other F-series cameras!
I had a Nikon Series E 35mm 2.0 years ago. I remember it didn't last very long as the plastic element used in it fogged up (became opaque) and the lens itself started falling apart (glue seemed to be used in the focus ring parts). It did have a metal lens mount though. The mount was the only thing that lasted on that lens!