Help with an older Tamron 200-400mm f5.6

It look's to me that you have a slightly bad copy of this lens.

I have the Tamron 200-400mm f:5,6 for Nikon, have had it since e'h forever i think.

I have used it in combination with Nikon F4 D2x And on Canon 350D 400D 5D with adapter. It works perfect, only problem i have had is focus hunting in low light and at the long end (350-400mm)
Most of the time i use manual focus.

Focus on infinity on my lens is to the other side than your's. Mine will focus past the moon.
But it's a sharp lens, and lightweight

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I'm narked what's your excuse