So it appears it's not a general problem for these Chinons. Interesting.
Here's what my Chinon 50/1.7 (S/N C638519) thinks is a white sheet of paper, complete with messed-up aperture:
By contrast, an A 50/1.7:
And an M 50/1.7:
And for kicks, a single-coated mid-'70s Porst (Cosina) M42 affair (6 elements / 4 groups, very Biotar-ish bokeh):
I'd say if you're falling way behind a single-coated lens in transmission, you've got a problem.
Now for the 1.4s.
Revuenon (Chinon OEM) 50/1.4, S/N C627455:
- vs. -
XR Rikenon 50/1.4:
Finally, a shot of coating reflections, Rikenon P vs. Chinon 50/1.7:
Those should correspond to the bottom and top Auto Sears in
#2, respectively. (The Rikenon P actually happens to be among my very clearest lenses, btw, at least on par with the A 50/1.7.) My two Chinons (1.7 and 1.4) seem to share the same kind of coatings.
(All shot with AGFA-labeled Chinon MC 28/2.8 @ f/5.6, manual WB.)