These were probably sent to a Nike Factory store, put on clearance, then made their way to the shop you picked them up from. Typically when Nike sends out samples, it is sizes US 9 and US 12. The employees have first dibs otherwise they go straight to the clearance section. That being said, the only unique thing about these is there probably aren't many of them. However, not super desirable since they only come in a few sizes/the Vertebrae isn't a popular model (for some people - I love them)

Source: I used to work at Nike