ONE PESO BUSINESS STRIKES
The One Pesos are the largest and the most popular of the US-Philippine series, and a number of the earlier dates are fairly easy to get nice. The 1904 is the most common. The 1904-S was a hoarded coin and just recently, a bag of them came on the market. Like the 1903 50 centavos, most of these coins were so covered with bag marks that they were lucky to qualify for MS-63. And even though the 1904-S is very common in low grade unc, there's only one graded gem by NGC or PCGS.
The key coin in the series is the 1906-S which was minted in considerable quantity and shipped to the Philippines. But before the coins were released, the price of silver had risen so sharply that the bullion value of the coins was greater than their face value, and so the coins were shipped back to America to be melted. Luckily, about a hundred coins were released into circulation and those are what formed the basis of the availability of these coins today. A wealthy Philippine collector from the 1980's through the early 1990's made a point of buying every genuine '06-S peso that came to auction in the Philippines. But, unfortunately, this collector liked his coins shiny so he cleaned them, and not gracefully either. So not only are these coins extraordinarily scarce because there were only a hundred of them that were released into circulation, but also because the majority of them were cleaned.The '06-S Peso, along with the '18-S 5 centavo mule, and the '03-S 50 centavos are the 3 crowned jewels of any USPI collection. Even in MS-60, these are $20-$30,000 coins. The '11-S and '12-S are the semi keys, and the '12-S is particularly hard.