There were three versions of this lens. The last is reported to have
the best optics. The first two have 15 elements in 10 groups. The
3rd has 12 elements in 9 groups. The 3rd is reported to have better
optics. The serial numbers for the first version ranged from 101911 to
192626, the second ranged from 210001 and upwards. The serial numbers
for the 3rd version started at 760801. You can recognize the 3rd
version because it has a metal cover on the back with a square shapped
hole to allow the light to exit.

I own the F4.5, 3rd version of this lens and I did own the 80-200 F4.0
lens. I found almost no differences. The books say the 4.0 has
less vignetting, but I did not notice it.

MK Stenstrom "Michael K. Stenstrom"