A cyberdog or "Cyber-Hound Mk. II, Personal Security Model" that belongs to Dr. Henry. As payment for assisting him with field work for the mutagenic serum as part of a quest, Henry activates the cyberdog for the Chosen One.
According to the Fallout Bible, at some point after the destruction of Control station Enclave, Henry attempted to destroy a cyberdog named K-9 who was in Dorothy's care, fearing that too much information about the Enclave could be obtained from it.[Non-canon 1]
↑Henry: "You'll be participating in an important experiment, in fact, the most important, scientific-oh, you mean money. Well, I do have a Cyber-Hound Mk. II, Personal Security Model, that I brought with me. I suppose I could have it activated and on-line by the time you got back. Would that do?" (Dr. Henry's dialogue)
↑Fallout Bible, K-9 (from Navarro): "After getting his motivator repaired, K-9 was left in NCR by the Chosen One so that he could receive necessary repairs from Dorothy and, not long after his recovery, Dr. Henry (who had been placed in critical condition after being reportedly assaulted by the Chosen One some time earlier). Dr. Henry, afraid that too much information about the Enclave would be obtained from K-9, attempted to destroy the cyborg, but was stopped by cyberdog and Dorothy, who suspected what Dr. Henry was planning. The NCR government used the attack as an excuse to confiscate K-9 and cyberdog in order to learn more information about the Enclave as well as what makes the two of them "tick." At last report (and over Dorothy's objections), K-9 and cyberdog were disassembled and analyzed. Structural damage during the disassembling is reported to have killed them both."