The f/2 lens is often seen marked as Nikkor-O. From what I can learn, this is an F-mount lens and the "O" indicates that it has 8 elements. And this is a quite desirable lens
The f/2.8 lens is marked Nikkor-S, where the S denotes a 7 element lens. This is a less expensive (and more recent) alternative to the above.Tom's Digital Photography Info / tom@mmto.org