Exist across the era "Sealed Chests" is, it is possible to obtain a better item by the light of the following procedure. In addition, it opened the "Sealed Chests" in the previous era, in the era after the "Sealed Chests" is empty. Therefore, in order to get both items, you have to open "Sealed Chests" in later times, then open "Sealed Chests" in the previous era later.
Examine the Sealed Chest in the previous era.
Answer "no" to the choices, not open the Sealed Chest.
Go to the later times and open the same Sealed Chest.