Although there are several non-U.S. mono releases of
Francis A. & Edward K., it may have been issued in mono in the U.S. only as a white label promo LP (F-1024).
Added: But, I did find this February 3, 1968
Billboard review, which lists the mono catalog prefix.
After that album,
Cycles,
My Way,
A Man Alone,
Watertown and
Sinatra & Company were also issued with mono catalog designations outside of the U.S. These are probably fold-downs of the stereo mix.