The one I played with is the MF version and the built is rock solid. I am not familiar with the af huan.
The old Vivitar primes circa late 70s- early 80s were a bit lackluster, but decent performers. I'm not sure if you would like it considering the pedigree you've already been exposed to. Have a look at the Zuiko 135mms. Even the lowest end f/3.5 version, wide open, and across all apertures, outresolves the EF 100mm 2.8 USM macro slightly closed down, and across all apertures.
The OM 135s can usually be gotten for dirt cheap. However, the f/3.5 version is a bit low in contrast, and generally the fatest in the group may not be the sharpest, so I would suspect the f/2.8 version would be the best balance.
... Allllooo hall bbbuttie and buttees.. time por Monlay brewz hergain.... haiz...
tired , think tml AWOL
Say gd morning to my OL
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moanin butties... enjoy the week ahead...