Ron Guth:
The 1904 Morgan Dollar presents a real challenge for the collector because of the general poor quality of the coins from this year. This defect has been known for decades (for example, in 1992, Dollar expert Dean Howe wrote: "...the 1904-P is among the worst coins produced at the Philadelphia Mint. Most 1904-P dollars have a subdued gray luster that is often dull and unattractive..."). Certainly, there are plenty of Mint State examples to go around (PCGS alone had certified over 4,000 Mint State 1904 Dollars as of April 2012). However, the real challenge is to find a nice-looking one.
Because of the poor quality of coins from this year, it should come as no surprise that Prooflike 1904 Dollars are very scarce. Even more rare are the Deep Mirror Prooflike versions, all of which are tremendous condition rarities.
The finest 1904 Dollars certified by PCGS (as of April 2012) include 15 PCGS MS66s, 1 PCGS MS65PL, and 1 PCGS MS65DMPL.