A machine left by the extinct Old Ones of Exo III that builds an android replica of a living person, complete with memories, on a spinning table.
The android duplicator is ancient equipment found by the archaeologist Roger Korby in the caverns of Exo III. It appears in the original series episode What Are Little Girls Made Of?
The subject lies on one side of a large turntable with a blank android form on the other. As the table spins at speed, the blank takes on the person's exact appearance and a copy of the mind. Korby has used it to make the androids Andrea and Brown, with the help of the surviving ancient android Ruk.
Korby duplicates Kirk, intending to place androids throughout the Federation. Kirk plants a crude insult to Spock in his own thoughts during the process, which alerts Spock when the copy repeats it. Korby himself proves to be an android, his original body having been dying of frostbite.