”under correction” goes from 0(sharp) to 3(more aberration)
from the book "Photographic lenses' basics and developments"
by Toshinobu Oguara ISBN4-257-12012-6 C0072 P2000E

It is optically Tessar type with two meniscus lenses, which act
as an spherical aberration inducer. Kinda expensive lens, hahaha