These are the 2 stems for comparison.



One Cinelli logo insert is flush with the leading edge contour, the other recessed.



Left expansion bolt is black anodized aluminum, with a gold anodized aluminum conical expander with a stainless steel threaded insert installed. The stem is super light with this setup.

The angled wedge quill is the standard Cinelli chromed steel bolt, with a diecast (zinc alloy?) wedge block. This stem is much heavier feeling of course.

The aluminum expander and bolt could be an old school aftermarket accessory, I do not know.