1866 was a transitional year for U.S. coins, with the big change being the addition of the motto "IN GOD WE TRUST" to most gold and silver coins. The authorizing legislation for this change was the Coinage Act of March 3, 1865, which ordered that the motto be placed on all gold and silver coins that "shall admit the inscription theron" (which, in layman's terms, means those coins that were large enough to accept the motto without it being too small or crowding out the design). Compliance with the Act of March 1865 meant that new dies had to be prepared at Philadelphia, not only for their internal use, but for the use of the branch mint at San Francisco. Unfortunately, new With Motto reverses were not sent to San Francisco until March 1866. In the interim period between January 1, 1866 and the arrival of the new dies, the San Francisco Mint produced a small number of 1866 Half Dollars with the old No Motto reverse (still in stock from the previous year). The result is a bit of a rarity in the series -- a date which is hard to find in any condition, and extremely difficult to locate in Mint State.
For many years, the finest 1866-S No Motto Half Dollar was the PCGS MS65, which was later upgraded to MS65+. However, in 2013, portions of the Eric P. Newman collection hit the market. Included in that collection was a stunning NGC MS67 example of this date. That coin, since crossed to PCGS MS67, now resides in the Simpson Collection and it remains the undisputed leader of the PCGS CoinFacts Condition Census.