A junk-bin Nikkor 135mm f/2.8 AI revived

The Nikkor 135mm f/2.8 AI was released ~1979, and whilst it seemed to have been shadowed somewhat by its 105mm f/2.5 AI-S sibling, still had a lengthy production run stretching into the early 2000s. Whilst I didn't have a need for this focal length, when I saw a junk condition lens for £15, it was hard to turn down even if was just to tear it down to see how these lenses worked.