knuckle_duster has definitions from the field of arms
1
[ noun ] (arms) a small metal weapon; worn over the knuckles on the back of the hand

Used in print

(Kenneth Allsop, The Bootleggers and Their Era...)

Until 1924 O_'_Banion pistoleers and knuckle-duster bullyboys had kept his North_Side domain solidly Democratic .

Related terms

weapon

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