49 CFR § 180.415 - Test and inspection markings.
(b) Each cargo tank must be durably and legibly marked, in English, with the date (month and year) and the type of test or inspection performed, subject to the following provisions:
(1) The date must be readily identifiable with the applicable test or inspection.
(2) The markings must be in letters and numbers at least 32 mm (1.25 inches) high, near the specification plate or anywhere on the front head.
(3) The type of test or inspection may be abbreviated as follows:
(i) V for external visual inspection and test;
(ii) I for internal visual inspection;
(iii) P for pressure test;
(iv) L for lining inspection;
(v) T for thickness test; and
(c) For a cargo tank motor vehicle composed of multiple cargo tanks constructed to the same specification, which are tested and inspected at the same time, one set of test and inspection markings may be used to satisfy the requirements of this section. For a cargo tank motor vehicle composed of multiple cargo tanks constructed to different specifications, which are tested and inspected at different intervals, the test and inspection markings must appear in the order of the cargo tank's corresponding location, from front to rear.
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