64. The obverse and reverse spotting kill the grade. I also recommend you conserve that coin - it looks like organic debris (from a sneeze or something), and will actively corrode your coin. After conservation (assuming it is successful), the coin may go as high as 65 or 66.
PR-64. As far as concervation, the milk spots on the reverse are part of the coin and cannot be removed through conservation. Some of the light hazziness could be removed, but I don't believe the grade would change. The spots on the reverse would likely limit the grade anyway.
Did it spot in the holder? The early NGC would probably never give a 66 to that coin if they knew it had those spots.