The designation, F84-CKX, also looked bogus (the dash number is in the wrong place, this was reportedly an F-84B, and the "X" should be a prefix, not a suffix):
But it turns out to be the real deal as reported by Bruce Craig (an F-84 subject-matter expert) Tom Chee, and other sources.
According to Bruce's blog, now gone from the internet as best I can tell, 80 F-84Bs were transferred to the Navy from the Air Force for use as target drones, designated F-84KX and given BuNos 142269-142348.
Tom notes that the official designation was "F84 KX" and Navy service histories only exist for the following Bureau Numbers:
142269: Assigned to NADC Johnsville from 28 October 1954 until it was retired on 9 August 1955. It was stricken in February 1956 with a reported total flight hours of 0 (if correct, it was a non-flying prototype for remote-control system installation and ground-based testing).
142270: Assigned to BAR (BuAer Representative) Cherry Point, North Carolina on 22 December 1954 and transferred to NADC Johnsville on 1 March 1955. It was retired on 9 August 1955 and stricken in February 1956 with a reported total flight hours of 2, which might be the ferry time from Cherry Point.
142271 and 142272 had virtually identical calendar milestones and the same flight time, 2 hours, as 142270.
My guess is that the Navy wanted to utilize a target drone with more performance than the F6F Hellcats being used at the time (an article in the July 1951 issue of Naval Aviation News stated that an F6F-5K was being modified by NADC to add two externally mounted turbojet engines "to increase its altitude range and speed maximum to provide gunnery targets comparable to today's faster and higher altitude fighter and bomber aircraft". The Air Force had replaced the F-84B in service by 1952 so it was available for the purpose.
The Navy apparently decided subsequently that it was beginning to have its own fleet of surplus jet fighters and it was more sensible to convert them to be targets than to add another airframe and engine to its logistics, training, and maintenance burden.
For a discussion of the color scheme and the fuselage length difference between the F-84B and the E/F, see https://tailspintopics.blogspot.com/2019/08/us-navy-f-84-thunderjet-target-drone.html
