FIVE CENTAVO BUSINESS STRIKES
The 5 Centavo business strikes are one of the hardest in the US-Philippines series to complete in unc. It has several stopper dates, headed of course by the famous 1918-S "Mule", which is comparable to the 1906-S Peso in difficulty. The 1906-S Peso is just a tad harder and a tad more valuable.
But still, the 1918-S Five Centavo "Mule" in AU-58 is a $10,000 plus coin and, there aren't many of those, even in 20th century US coins. And even at those prices, the 1918-S Five Centavo "Mule" is a great rarity. It's comparable to the 1918/17 Buffalo
5 Cent piece, which in the top grades, goes for $250,000.
The regular 1918-S is also difficult, but under-rated because it is overshadowed by the "Mule". The 1916-S and 1919-S are also killer dates. The '16-S, '18-S, and the '19-S are so scarce in gem unc that if the Buffalo nickels are scarce, these are even scarcer. And the Buffalo nickels often sell for hundreds of dollars in the top grades.
The 1941-M Five Centavos are arguably the hardest of the regular issues in the commonwealth series. And the 1941-M, while not rare in unc is very hard in gem. In MS-66, when it's made, will probably be the first $10,000 commonwealth coin.