Number Ones was first issued with custom-art inner sleeves for both the LP and EP. The artwork is the same that was used on the international Beatles release, 20 Greatest Hits. At a later stage of production, the custom art sleeves were withdrawn in favour of a standard polythene bag for the LP, and a generic EMI paper sleeve for the EP.

Because the original inner 'art' sleeves were identical for LP and EP, albeit scaled to suit each format, the scan of the first EP sleeve, below, serves to typify the sleeves of both.

By the time of the 'EMI Music Group Australasia' pressings, the 'art sleeves' had been replaced with a plain poly bag (LP) and standard EMI paper sleeve (EP). To date, green and yellow generic sleeves have been verified.
The Number Ones - EP - Style 'A' (EMI Music Group Australasia) - Generic EMI sleeve (yellow)

Two known variations of the 'art sleeve' exist; one with a central hole and the other without.
The Number Ones - inner sleeve art (EP)