My son has been using the Rokkor 135 f:2.8 (mid 70's vintage) on extension tubes. He has gotten excellent results near 1:1 and lower reproduction ratios. We looked at slides taken with that combo side-by-side with Olympus 90mm macro shots (about 1980 vintage lens) and 100mm f:4 Macro-Elmar shots, and his work looked just fine by comparison. The person shooting the Oly macro wasn't expecting much, he's a professional photographer who's done extensive macro work over the last 20+ years, and was impressed by the Rokkor's performance.
I know this thread is old but it's the "macro forum", so I'd like to add to this post: Back in the late 70's, the 100mm f3.5 MC Rokkor macro lens (helical focus) was deemed "the best macro lens ever tested of all those tested to date" (at the time). It was a bold statement made by someone testing/comparing macro lenses for a major photo magazine.
"Pictures are not incidental frills to a text; they are essences of our distinctive way of knowing." Stephen J. Gould