The Gemini-Era “Celestial Display Device” shown above (Serial No. CF55061/CF55061-2) comes from the personal collection of Apollo 7 LMP Walt Cunningham, and was used in astronavigation training during the early Apollo Program. 
 
The device consists of two pieces: 1) an open-ended translucent outer sleeve with the orbital period printed down the center; and 2) an accordion-fold star chart showing the constellations, centered along the celestial equator.  
 
On the Apollo missions, a set of 45 stars were used for navigational purposes. On the star map insert, Cunningham has underlined these stars in red, also writing in the names of three unlabeled stars: Navi, Dnoces, and Regor.  These stars—based on nicknames for the Apollo 1 crew members (spelled backwards)—were added to the list of early Apollo navigational stars by Gus Grissom.  After the loss of the Apollo 1 crew in a launch pad fire in January 1967, NASA made these star names official. They appear on all subsequent Apollo star charts and navigational star lists.  
 
Slide-rule style orbital devices such as this one were used extensively during the Gemini Program, but were only used as training devices in Apollo. 
 
In his certification letter, Cunningham mentions that he carried and used this device during night flights in his T-38 prior to the mission.  In training, many astronauts would practice star identification during night flights, looking through empty paper rolls in order to realistically restrict their field of vision.  
 
This unique training-used item was first offered for sale at auction by Lunar Legacies. It comes with signed COAS from Walt Cunningham (x2) and Don Willias (Founder, Lunar Legacies).