Possession of Slungshots, Billies, Sandbags and Brass Knuckles in New York
In People v. Persce, 204 NY 397, 97 N.E. 877, 27 N.Y. Cr. 41 (1912), the court held that mere possession of an item known as a "slungshot" was criminal and that proof of intent to use the same was unnecessary.
In so holding, the Court state " the well understood character of slungshots, billies, sandbags and brass knuckles make it evident that the legislature were entirely justified in regarding them as dangerous and foul weapons seldom used for justifiable purposes but ordinarily the effective and illegitimate implements of thugs and brutes in carrying out their unlawful purposes." (Id at 402.)
Thus the Court of Appeals has already recognized that brass knuckles have "well understood" characteristics.
It is further important to note that all of the weapons referenced by the court as having "well understood character," including brass knuckles, lack a specific Penal definition.