Slaver stasis box

Slaver stasis boxes were priceless artifacts, the only remains of the Slavers, which ruled over most of the Milky Way galaxy one billion years ago. A temporal stasis energy field preserved the contents of a box, which could be opened with a stasis field nullifier. Spock described the effects of stasis boxes on Federation science as “incalculable.” For instance, artificial gravity aboard Federation starships resulted from Slaver technology, from a box containing an anti-gravity belt.

Overview
A Slaver stasis box was a cube, 50cm per side with a silvery mirrored surface. It was described as “a mirror-sided cube twenty inches on a side” in the episode’s final draft script, though it appeared yellow and sometimes rectangular onscreen. A stasis box could locate another box within a few light years, with a glowing teardrop pointing the way. 

One box contained a printed photograph of a Slaver (a simuhologram in the novel), protoplasmic meat (wrapped in a metal-ceramic polymer in the novel), and the mysterious Slaver weapon, a multi-purpose device with settings for a portable telescope, laser, energy absorber, personal rocket-motor, and an artificial intelligence interface. It also had a setting for a total-conversion beam, a weapon of mass destruction. (episode)

History
Opening a box could be dangerous. One contained a live disruptor bomb. (episode) When one was put into an excavating crusher, the pressure triggered a defensive reaction, encasing the person responsible within a stasis field. (novel) One contained fresh but poisonous meat. Because of the risks, Starfleet assumed jurisdiction over the boxes, allowing “only certain key specialists” to open them. (episode)

Only one box had been found within Klingon space. Nonetheless, Klingon Captain Kumara was familiar with them, and went to great lengths to steal one. (novel)

One box found by Kzinti archeologists was either empty (episode) or contained nothing of value (novel).

“Of the dozen stasis boxes found during the Federation’s history, this (the one being taken to Starbase 25 aboard the Copernicus) is the fifth to be found on Kzin itself. This seems confirming evidence that the planet was once an important military base of the Slaver species.” (Unaired portion of Spock’s log entry, final draft script, dated 7/23/73)

Stasis fields were used in stasis boxes and other equipment in the 24th century.