The production history of the Super Sabre came to an end when the last F-100F two-seater was delivered. However, there were several other Super Sabre variants subsequent to the F-100F which were the subject of serious design studies but which never saw the light of day.
For some odd reason, the designation F-100G and F-100H were never assigned.
The F-100J (probably J for Japan) was the designation given to a projected, but unbuilt all-weather interceptor version offered to Japan through the Foreign Military Sales program. The Japanese government expressed no interest, and the project proceeded no further than the concept stage.
F-100K was to have been a version of the two-seat F-100F in which the J57-P-21A was replaced by the J57-P-55. This version was never built.
F-100L was to have been the designation of an equivalent J57-P-55-powered version of the single-seat F-100D. This version was never built either.
The designation F-100M was never assigned.
The F-100N (probably N for NATO) was to have been a "stripped" version of the F-100D with simplified electronics that would be offered to the air forces of NATO nations. It attracted little interest and was not proceeded with.
The designations F-100P,Q, and R were never assigned.
The F-100S (probably S for Spey) was a 1964 proposal for a F-100F airframe powered by a Rolls-Royce RB.168-25R Spey turbofan. North American had hoped to establish a production line in France for two hundred examples of the F-100S, but nothing ever came of the idea, and no F-100S was ever built.