Is it illegal to purchase an aluminum knuckle duster bottle opener

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If a client sends me a piece of aluminum they own and pay me to mill their property (the piece of aluminum) into a pistol receiver, is that illegal? I know selling

If brass knuckles aren't made of brass, are they still illegal? - Quora

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Is it illegal to purchase an aluminum knuckle duster bottle opener? I'm in Canada and the product would be coming from the states. - Quora

Is it illegal to purchase an aluminum knuckle duster bottle opener? I'm in Canada and the product would be coming from the states. - Quora

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