27 C.F.R. § 26.164a
When required in this part, with respect to Puerto Rican spirits, a package gauge record shall be prepared to show:
(d) For each package, the:
(7) Proof.
(Approved by the Office of Management and Budget under control number 1512-0250)
[T.D. ATF-198, 50 FR 8551, Mar. 1, 1985]