the.com/knuckleduster
A ring with ambitions, designed to make your fist legally regrettable.
means A metal hand weapon worn over the fingers to concentrate a punch's force into something far nastier.
from American slang from the 1850s, blunt and literal: it dusts knuckles, or rather, dusts whatever your knuckles meet.
Brass mythOften called brass knuckles but rarely actual brass.
Trench eraWWI soldiers carried knife-knuckleduster hybrids into close combat.
Banned widelyIllegal to carry in many countries, including the UK.