ATF Ruling 79-9
The Bureau of Alcohol, Tobacco and Firearms has recently recognized the need to establish guidelines for use of the terms "Original Proof," "Original Barrel Proof," "Entry Proof" and "Barrel Proof" on distilled spirits labels.
No standard definitions have been issued by the Bureau specifying when and under what conditions distilled spirits labels may bear phrases indicating that the proof of the spirits when originally produced and when bottled is the same. Previously, the Bureau commented on the use of terms such as "Original Proof," "Original Barrel Proof," "Entry Proof" and "Barrel Proof" on a case-by-case basis.
Although these terms are to defined in the regulations, they have acquired certain meanings when used on distilled spirits labels.
To preclude any misunderstanding and to effect standardization in the use of these terms, the Bureau is issuing guidelines as follows:
Held, a distilled spirits label bearing the phrase "Original Proof," "Original Barrel Proof" or "Entry Proof" indicates that the proof of the spirits entered into the barrel and the proof of the bottled spirits are the same.
Held further, "Barrel Proof" on a distilled spirits label indicates that the bottling proof is not more than two degrees lower than the proof established at the time the spirits were gauged for tax determination.
27 CFR 5.33(f).