27 CFR § 19.494 - Additional marks on portable containers.
(a) In addition to the other marks prescribed in this part, a proprietor must mark portable containers of spirits or denatured spirits (other than bottles enclosed in cases) that will be withdrawn from the bonded premises as follows:
(1) Without payment of tax, for export, for transfer to customs manufacturing bonded warehouses, for transfer to foreign trade zones, or as supplies for certain vessels and aircraft, in accordance with the provisions in part 28 of this chapter; or
(2) If tax-free, with the word “Tax-Free.”
(b) A proprietor may show other optional information such as brand or trade name; a caution notice, or other information required by Federal, State, or local law or regulations; wine or proof gallons; and plant control data. However, any such mark must not conceal, obscure, interfere with, or conflict with the markings required by this subpart.