The first MK2s came out with lenses that didn't have an AR coating. When the AR lenses came out I got one, but it also causes slight bluriness. Although the AR lens isn't bad, I prefer the original one, smooth/reflecting one. It's a compromise you make, I'm pretty sure all AR coatings will cause at least a little bluriness.
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(list 6284, Mk1 S/N 00299 4GB blue [sold]. Mk2 S/N 080000094 20GB blue)