If you look at the Christopher Perez/Kerry Thalmann lens tests, they show that the 1980's non-APO labeled version of the Rodenstock Sironar-N 135mm f5.6 arguably outperformed the later 1990's APO labeled version (see results copied below).
I note they often tested the same model and saw significant sample variation--do you think that is the case here or is the later APO version really though of generally as "less good"?
Also, confusingly he makes this statement about the APO Sironar-N 135mm even though the two lenses have different weights (185g vs. 170g):
"Also, for years, it was sold as the "plain" Sironar-N (no APO moniker). There was absolutely no design changes between the plain Sironar-N line and the current APO labeled line. This change was purely marketing hype."
Why the different weights if they are exactly the same?
Rodenstock Sironar N f/5.6 135mm
f/11 48 48 24
f/16 54 54 54
f/22 60 54 54
185g Copal 0 109xxxx2 1980's
Rodenstock APO Sironar N f/5.6 135mm
f/11 38 42 30
f/16 54 60 54
f/22 48 48 48
170g Copal 0 11369xxx 1990's