There appear to be two different versions of some or all items on the steam market. For example, the Formal Body Shell: I can find one page for it here, and a different one here. The latter is the only one that shows up when I search for it, but if I just browse through the listings I see both. This applies to a lot of items, but is easier to see with higher rarities.
EDIT: the bug appears to be that each item is listed under its full name and its code name. Look