The value
- ex (Gen III, lowercase)
Where it comes from
The line in the source
This set is also the first to have Pokémon-EX, Pokémon who are stronger than usual, but the opponent takes 2 Prize cards if one were to be Knocked Out.
In English
Ruby & Sapphire (EN 2003-07-01, 109 cards). Wikipedia calls it Pokémon-EX; the era is the "ex" series.