I've been looking at paper money that appeared at auction though the years, sometimes I see a note that was graded by auctioneer as AU a couple of times, later it was graded by a major service at a much higher grade, sometimes I see the opposite, a CU65 downgraded to AU58. I wonder about the notes that were upgraded, were they repaired? How can something go from AU50 to CU 63-65?
Nothing stirs a collectors passion more then the subjective opinion of whatever it is they collect.......be it Fine Art, Vintage Automobiles, Antiques, Coins, Currency, and the list goes on and on. Grading is, and always will be a matter of opinion. The imprint on the holder simply states what an employee or employees of a particular grading service considered the note to be graded at a particular time. Because condition dictates prices, notes have been, and I'm guessing, always will be "improved upon" in order to raise the grade.
Well the grades I saw were graded by cataloger of major auction companies, I would think they would be experienced. The grading companies are either PMG or PCGS