Presented below are some detailed photos of a rare screen used crew crystal from the 2nd season Star Trek: The Original Series episode "By Any Other Name" (first airdate: Feb. 23, 1968). It is made entirely of styrofoam and measures approximately 5" x 5" in size. As described by Rojan of the Kelvan Empire (portrayed by actor Warren Stevens), these props are "the essence of what they [the crew members] were; the flesh, and brain, and what you call 'personality', distilled down into these compact shapes. An inexpensively created, yet central plot device of the episode...
A similar crystal as displayed at the 1992 Star Trek Exhibition at the National Air & Space Museum in Washington, D.C. ...
Some episode screenshots from "By Any Other Name" that feature these crystals ...