Ron Guth:
The 1875-S Twenty Cent Piece is the indisputable king of the series in terms of total mintage. Exactly 1.15 million were made, almost ten times as many as the 1875-CC, the closest challenger. As a result, this is the most affordable date in this short-lived series, and it is the best choice for type collectors because of the availability of high-grade examples.
Over a thousand Mint State 1875-S Twenty Cent Pieces have been certified by PCGS alone, including nearly two hundred in MS65. In MS67, this date becomes truly rare and the finest example tops out at PCGS MS68.
Keep an eye open for the S over S variety, which shows a repunched mintmark.