Ron Guth:
1884 was the first time that employees at the San Francisco Mint produced Dimes since 1877. They produced over 560,000 Dimes, which is not a small mintage, but because most of the coins went directly into circulation, it is hard to find this date in high grade. A couple of dozen examples are available in MS63 and MS64, with far fewer examples available in Gem (or better) conditions.
Dime researcher Gerry Fortin has identified six different die varieties for this date. All of these varieties are at least scarce and several are very rare.