You can't really tell from the picture, but actually per the original page it was actually 8-inch. You see, the MS-DOS disk is not for the IBM PC, but for the SCP 8086 card based S-100 system SCP 86-DOS was originally developed on before MS bought it. Anyone else remember it?
I may not remember correctly, but wasn't it that MS-DOS 4.0 was replaced by 4.01 two days later or so?
Also, typo below the MS-DOS 2.0 picture: It should be 5 1/4" (the floppy with the half one was 3 1/2").