I have a decent Peace Dollar in some NGC plastic and was just looking at my coins and noticed some odd doubling on a few letters in the motto on the reverse. What I am seeing I would typically call Machine or Mechanical Doubling, but its a bit sporadic on this one and not on consecutive letters or very consistent. I am seeing it on the UNIT D of 'United', the STA of 'States' and then on the E P U of "E Pluribus'. It looks like shelf doubling, but I wanted some info or direction on where to check to possibly identify this for sure. I am probably not going to be able to get any decent photos but I will try. Has anyone else ever come across anything similar?