The SS Deirdre was an Ptolemy-class transport in service during the 23rd century. (Ship Recognition Manual, Volume 4: Starships of the Original Series Era) The Deirdre performed cargo and courier runs near the Capella system. In 2267, the Klingons issued a false distress call claiming to be the Deirdre to lure the USS Enterprise away from the system. (TOS: "Friday's Child")