Charleston slave badge from 1838 for Porter No. 758

This is a square metal slave badge set on point with clipped corners. On the recto is text that reads” CHARLESTON [stamped]” across the top. Under that is “1838 [stamped] / PORTER [stamped]/ 758 [punched].” There is a small chip out of the top proper right edge. There is a hole punched at the center top.