135mm Legacy Lens opinions wanted

I'm considering buying a 135mm lens (to use on my NEX-6). I'm looking at a Pentax M 135 f/3.5 and also a Minolto MD ROKKOR 135 f/3.5.  I know something about the legendary Pentax quality, but not this lens.  And the Minolta 135's are pretty cheap - which makes me concerned.

But I'm not stuck on anything, I have no experience with the Canons or Nikons in this range.

So if you have some knowledge/experience regarding 135mm legacy lenses, feel free to share. Thanks in advance.

--
Hey, it ain't rocket surgery.
Larry
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