Sealed
Keep your cancel card
This file is what lets you destroy the locket before it opens. Treat it as a secret: anyone who has it can permanently destroy this locket. Do not send it with the locket.
Keep your key half
This file is the other half of the key, and the locket cannot be opened without it — by anyone, including you. Save it somewhere you will still have on the unlock date.
Do not send it before the unlock date. Anyone holding this file and the locket together can open the locket immediately. Not sending it is how you call the locket off; there is no cancel button in this mode.