In case anyone is doubtful, it is indeed 24fps for "Rear Window"
The fps setting is in the "Project" properties.
The origin of 24fps as a standard is not entirely clear.
Film historian Kevin Brownlow says that while early silent filmmakers settled on about 12-16 fps as a rough target, theater owners soon began to project films slightly faster so they could get an extra show in each day. Filmmakers countered by shooting faster and theater owners countered back. This arms race continued all through the 20's until sound came in.
A solid standard HAD to be adopted for sound and 24 fps was chosen as an average of the prevailing projection rates at that time. It probably helped that 24 frames of film was exactly 1.5 feet and for animation it turned out well because 24 was evenly divisible by 2,3,4,6,8 and 12.
29.97 for NTSC... that's got to be one of the biggest design mistakes of the 20th century but we have to live with it.