This version of Supreme is most easily distinguished from others by his behavior, memories of being an early ally of Superpatriot and the shape of his wristbands and chest brand. Mean supreme has comparatively streamlined wristbands and his chest brand is rectangular in shape, calling back early renditions of Supreme in the 1990s.
While is is the original supreme by some perspectives, including arguably a “meta” perspective, he is explicitly not the same character that starred in issues #41-#63 of the Supreme solo book. Nor is he the “Original Supreme” character introduced in #41 and seen in most issues from #64 to #68, more often than not as an actual foe of Mean Supreme.
The matter is complicated somewhat because the issues before the Alan Moore run dealt extensively yet independently with appearances of alternate versions of Supreme.