Token cards have actually been around since as early as the Unglued set. Generally tokens have been created in response to a card that is released for an expansion that mentions a specific token type.
Since this is Soldier week, we've gone into the art archives to track down the three different soldier tokens and show you the images from these token cards.
The Three Soldier Tokens
The first soldier token actually appeared in the Unglued set.
The second soldier token was in fact a goblin soldier token. It appeared with Apocalypse to play with the card Goblin Trenches.
The third soldier token was required with the release of the Onslaught expansion in order to play with the card Mobilization.