typically nitto's heat treated alu bars are sleeved, which is the 'spacer' in the photos with those bars mounted up in the stem. it's not an extra piece. i don't know what's up with the other set, it looks like either the sleeve was removed somehow, or they were clamped in a wide stem like a thomson elite and just rubbed clean on either side by hands.

without looking at the markings it's hard to say whether those are a version of nitto ADB-X or a copy.