JIS semiconductor designation

Japanese Industrial Standards (JIS) has standard JIS-C-7012 for semiconductor part numbers. The first digit denotes the p-n junction count ("3" may also denote a dual-gate FET); then follows the letter "S", then: Then follows the Japan Electronics and Information Technology Industries Association's Electronic DEvice REgistration Center (JEITA-EDEREC)-assigned part number, optionally followed by suffixes (such as "A", "B", "C", or "R", "O", "BL", standing for "Red", "Orange", "Blue" etc.) to denote variants, such as tighter hFE (gain) groupings.

Source: Wikipedia — JIS semiconductor designation (CC BY-SA 4.0)