Well technically the coins are either Mint State or Proof, so calling one MS55 isn't entirely wrong, just not common in numismatics. All the numbers are just definitions of wear below 60 and definitions of contact marks above 60. When Dr. Sheldon came up with the grade numbering system we use today, it was designed for Large cents and based on a value. (And from what I understand only went to 70 due to Sheldon's affinity for the number 7). His original system was created in 1949 and published in his book "Early American Cents" page 29 begins with the condition of a coin and on page 30 he describes the terms to apply them to - being;
Fair
Good
Very Good
Fine
Very Fine
Extremely Fine
Uncirculated
(also note again 7 descriptions, following Sheldon's 7 theme). I find it interesting Sheldon leaves out AU but then refers to Almost Uncirculated coins or AU50 coins a few pages later.
The Saddle Ridge Hoard coins are amazing, and I thought I would get one myself, but at the prices they are selling for initially, I think not. They will come down to closer to market pricing soon enough, might take a year or two before the hype wears off, and it's just another label on a slab (I hope). The prices they are asking on them seem to be - really a bit much, like TV Coin pricing much!
Thanks for the photos of the hoard coins home at their birthplace.

"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013!
ANA Life Member #3288 in good standing since 1981, ANS, Early American Coppers Member (EAC), Colonial Coin Collectors Club member (C4), Conder Token Collector Club member (CTCC), Civil War Token Society (CWTS) member, Liberty Seated Collectors Club (LSCC) & Numismatic Bibliomania Society member (NBS), USMex, Member in good standing, 2¢ variety collector.
See my want page:
http://goccf.com/t/140440