Charleston slave badge from 1858 for Mechanic No. 450

This is a square metal slave badge set on point with sharp corners. On the recto is text that reads ”CHARLESTON [stamped]” across the top. Under that is “1858 [stamped] / MECHANIC [stamped] / 450 [punched].” The ‘Charleston’ stamp was unevenly applied. There is a hole punched at the center top.