504.2.

Face-down spells on the stack, face-down permanents in play, and face-down cards in the phased-out zone have no characteristics other than those listed by the ability or rules that allowed the card, spell, or permanent to be turned face down. Any listed characteristics are the copiable values of that object's characteristics. (See rule 418.5, "Interaction of Continuous Effects," and rule 503, "Copying Objects.") Objects that are put into play face down are turned face down before they come into play, so the permanent's comes-into-play abilities won't trigger (if triggered) or have any effect (if static). Objects that are played face down are turned face down before they are put onto the stack, so effects that care about the characteristics of a spell will see only the face-down spell's characteristics. Any effects or prohibitions that would apply to playing an object with these characteristics (and not the face-up object's characteristics) are applied to playing this object.