There is one monster 1906-S double eagle and it may not be listed in the PCGS CoinFacts census. It's the Eliasberg-Clapp coin, sold at the Eliasberg sale in October, 1982. Gordon Wrubel and I bought the coin at that sale for what was a big price at the time, $16,500. We graded the coin MS68! The PCGS Pop Report shows one MS66, with none higher. Is this the Eliasberg coin? Maybe...maybe not.
Here's what happened to the coin in 1982. My long term partner Van Simmons sold the coin almost immediately after Gordy and I bought it. It was a very strange transaction. A guy calls us and says he wants to buy some great coins. He shows up at our office with about $100,000 in cash, He bought the 1906-S $20 and some other super coins. We didn't know the guy, had never seen him before, and we have never seen him or the coin since!
The 1906-S is a relatively common date, similar in overall rarity to the 1889-S, 1894-S, 1895-S, 1896-S and 1903-S. It is not as rare as the 1901-S or 1905-S nor is it as rare in Unc. as the 1902-S. The 1906-S is not especially hard to find in Unc-60 but it is moderately scarce in choice Unc. Gems are very scarce and I doubt if more than a few superb uncs exist.