The KIT uses the Westcott and Hort Greek text as the basis for its translation. When the KIT was published by the ORG, I believe that its cost to the public was a mere $5-7....where else could you get a copy of the orginal greek for so cheap?
If Mantey carried it around as he traveled, as Martin states, it was probably for two reasons....1) Because it was a verifiable copy of the original text by W&H and therefore reliable for study, and 2) It proved entertaining on long trips like a video of failed motorcycle jumps