I never realized phasing was so popular in the early days of Magic.
Just like Oubliette before it, Antiquities' Tawnos's Coffin was created as a way to remove a creature from the game temporarily. The creature could let out of the coffin at which point it would return to play in tact, complete with counters, enchantments, and so on.
Modern rules state that a creature that is removed from the game has no memory of ever being in play… so how does the Coffin handle such interactions under Sixth Edition rules? With phasing.
The Oracle wording reads:
You may choose not to untap Tawnos's Coffin during your untap step.
: Target creature phases out. It can't phase in as long as Tawnos's Coffin remains tapped. When Tawnos's Coffin leaves play or becomes untapped, the creature phases in tapped.
Phasing moves a creature to another zone (called the "phase zone") which behaves differently than the "removed-from-play" zone. Phased creatures remember all their characteristics and come back into play as if they never left.