RCW 9.41.250
Dangerous weapons -- Penalty.
Every person who:
(1) Manufactures, sells, or disposes of or possesses any instrument or weapon of the kind usually known as slung shot, sand club, or metal knuckles, or spring blade knife, or any knife the blade of which is automatically released by a spring mechanism or other mechanical device, or any knife having a blade which opens, or falls, or is ejected into position by the force of gravity, or by an outward, downward, or centrifugal thrust or movement;
(2) Furtively carries with intent to conceal any dagger, dirk, pistol, or other dangerous weapon; or
(3) Uses any contrivance or device for suppressing the noise of any firearm,
is guilty of a gross misdemeanor punishable under chapter 9A.20 RCW.
