[str]

You are right, the first 2.0/90 Summicrons, are two different designs
and the differences are as important as from the first to the second
2.0/50 Summicron. (I used all these four lenses and saw it looking
at the pictures - sometimes.) But in most collector's guides these
two first 2.0/90 Summicrons are counted as the first one. I suppose,
that the design changed with the change in the slowest aperture
from f. 16 to f. 22 and the slightly changed barrel.

The young man with the age near the Summitar.

Stefan