27 CFR 26.206: Marking packages and cases.

The distiller, rectifier, or bottler shall serially number each case, barrel, cask, or similar container of distilled spirits filled for shipment to the United States. In addition to the serial number of the container, the distiller, rectifier, or bottler shall plainly print, stamp, or stencil with durable coloring material, in letters and figures not less than one-half inch high, on the head of each barrel, cask or similar container or on one side of each case, as follows:

(a) The name of the manufacturer;

(b) The brand name and kind of liquor; and

(c) The wine and proof gallon contents; or, for bottles filed according to the metric standards of fill prescribed by § 5.47a, of this chapter, the contents in liters and the proof of the spirits.