From Bulbapedia, the community-driven Pokémon encyclopedia.
A retro card is a term used to refer to special reprints of cards from the early years of the Pokémon TCG which have been included as secret cards in the Stormfront, Platinum, Rising Rivals and Supreme Victors expansions. They can also refer simply to a card that was printed early on and then reprinted much later.
Common among them is their origin in the earliest sets of the TCG: so far, all those which have been printed are from Base Set and Jungle or are promotional cards from the first three years of the TCG's existence.
A special feature specific to these cards is their use of a gold-colored border and evolution box design, a striking contrast to other cards of the current era, which use silver-colored borders. This is, of course, a reference to the card design of the early expansions.
The art on these special re-releases is done by the same artist who did the original art, in a slightly updated manner.
List of retro cards