A chest is a wooden box with a hinged lid, often banded in metal and locked, used for the storage of valuables. Mundane heralds blazon it a “coffer” or “coffer box”; one Society armory blazons it a “casket”. It’s a period charge, found in the arms of William Cope (d.1513), cofferer to Henry VII [DBA2 215]. The chest’s lid is closed by default; in Society armory, it’s typically depicted affronty, but period examples (e.g. Bossewell, 1572 [III.16]) show it slightly in trian aspect, as in the illustration.
In Italian armory, there is also the cassa, “strongbox”, drawn as an unadorned rectangular metal box in trian aspect; it’s found in the canting arms of da Cassan, mid-15th C. [Triv 121]. For related charges, see Ark of the Covenant, coffin.
The Keeper of the Regalia for the Prince of the Sun bears: Azure, on a chest argent a fireball sable enflamed proper.
Oriana of Xylina bears: Gules, a blonde mermaid proper crowned with a pearled coronet Or maintaining a wooden casket proper and a mirror argent, a chief wavy Or fretty sable.