Command packet

From Memory Alpha, the free Star Trek reference

In the 23rd century, the command packet contained a copy of a starship's destination schedule, as well as the Captain's taped last orders. The packet itself was a black envelope emblazoned with the vessel's assignment patch and it was kept in the Captain's personal safe. A commanding officer would have it on hand during court martial proceedings, such as a preliminary hearing, but the packet would not normally be taken off the ship. (TOS: "What Are Little Girls Made Of?", "This Side of Paradise", "The Tholian Web", "The Menagerie, Part I")