In article <4fn5k0$j1c@nis.dacom.co.kr>, sj411@chollian.dacom.co.kr says...

>How can I tell a Nikon 50mm AIS lens from a series-E or non-AI lens
>only by its appearance?
>Please someone help me.
>Thanks in anticipation.

Nikon has made MANY "normal" lenses (for performance comparisons,
you may want to visit this site [stay tuned for physical appearance differences]):

D. Ruether's "SUBJECTIVE Lens Evaluations (Mostly Nikkors)",
which includes a listing of all Nikon SLR lenses ever made (with a
subjective evaluation of many of them, a general description of Nikkor
lens performance characteristics by lens-type groups, and comments on
particular lenses when the general descriptions plus the subjective
evaluation numbers are not sufficient to describe performance),
can be found at these sites:
-- Jan-jaap Aue: (nice text format)
http://www.phys.rug.nl/mk/people/aue/nikon/david.html
-- Bo-Ming Tong: (go to end of long article, plain text format)
http://www.cs.arizona.edu/people/bmtong/photo/nikon.faq
-- Quang-Tuan Luong: (plain text format)
http://robotics.eecs.berkeley.edu/~qtluong/photography/35mm/nikon-neuman
-- Niklas Nikitin: (nice table format)
http://www.cs.hks.se/~nicke/private/photo/david.html

The Nikkor 50's (all have 52mm filter size), MC = "multicoated":
- 50mm f2 (non-AI) is short and has a metal knurled focus ring
- 50mm f1.4 non-AI is chunkier and also has a knurled focus ring
(late versions had black rather than chrome fronts, and MC)
- 50mm f1.4 non-AI (late) is shorter, has a rubber covered focus ring,
MC
- 50mm f1.4 AI looks similar, but has the AI aperture ring (with
ridges at the rear edge of the ring, and the second set of small apertures at the back end of the ring), MC
- 50mm f1.4 AIS looks the same, but has the orange colored minimum aperture, and a "scoop" out of the rear flat face of the chrome
bayonette, MC
- 50mm f1.8 AI, AIS (metal) look the same as their f1.4 counterparts,
except that the front element is smaller, and set further back
in the mount, MC
- 50mm f1.8 AIS (plastic) is very short, is plastic-barreled, and
has an odd texture on the focus ring - and, unlike the above lenses, it has no metal clip at the f5.6 position on the
aperture ring, MC
- 50mm f1.8 E is the same size as the compact "plastic" AIS, but the
aperture ring either has a "blocky" imprint (and no chrome
ring to hold when mounting), or a thin rubber focus ring, and
a chrome holding ring like AI-AIS lenses
- 50mm f1.8 AF is longer, has a plastic barrel and has the footage
scale behind a plastic window, and has either a thin plastic, or (later) rubber covered focus ring, MC
- 50mm f1.4 AF looks identical to the 50mm f1.8 AF, except that the front element is larger and nearer the front of the lens, MC
- 50mm f1.2 AI-AIS is fatter and heavier than any of the above, MC
- 55mm f1.2 non-AI has a knurled metal focus ring, and is also fatter
and heavier than the above, some are MC?
- 55mm f3.5 Micro non-AI is long, has deep-set optics, and knurled
metal focus ring - early ones have a chrome front, very early
ones have a "compensating" diaphram, late ones have a
diamond-pattern focus ring and black front,and are MC
- 55mm f2.8 AI-AIS have rubber focus ring, MC
- 55mm f2.8 AF has a plastic barrel, thin plastic focus ring
- 58mm f1.4 non-AI loohs like the 50mm f1.4 early non-AI
- 58mm f1.2 Noct AI-AIS is very fat looking, otherwise it looks like
the 50mm f1.2, MC
- 60mm f2.8 Micro AF has a plastic barrel with rubber focus ring

I hope I got them all. (Of course, the printed words and numbers on
the lenses are your first indicators of the lens' identity ;-)
Hope This Helps