Historical Rules · 8 April 2016
Rule 711.1a
Official source text from the 8 April 2016 Rules release
A double-faced card’s front face is marked by a front-face symbol in its upper left corner. On cards in the Innistrad block and Shadows over Innistrad set, the front-face symbol is a sun. On Magic Origins double-faced cards, the front-face symbol is a modified Planeswalker icon.