The F-1 is at the left and the F-1N at right.
There apperances makes little difference between them, but in detail, next three are the major revisions.

Film wind lever
The operation arc of film wind lever decreased from 180 deg. to 139 deg. and this made film advance faster.

PC terminal
The PC terminal had a fastener to prevent the PC cord from disconnection.

Film type indicator
The film type indicator was added on the rear cover.