All gunpowder exceeding F1500 grams in weight, when publicly exposed for sale or sold, shall be in a substantial case, bag, canister, or other receptacle made and closed so as to prevent the gunpowder from escaping, and (except when the same is sold to any person employed by or on the property occupied by the vendor for immediate use in the service of the vendor or on such property,) the outermost receptacle containing such gunpowder shall have affixed the word “gunpowder” in conspicuous characters by means of a brand or securely attached label, or other mark.

If any gunpowder is sold or exposed for sale in contravention of this section—