The mark

Nine elements, in order

On this page11

One, the symbol Two, the identification code Three, the performance standard Four, specific gravity or mass Five, test pressure, or a letter Which means one character tells you liquid or solid Six, the year Seven, the country Eight, the maker Nine, thickness where it applies References

The order is fixed. Which is what makes it readable at a glance.

One, the symbol

The United Nations symbol "as illustrated in paragraph (e)(1)(i)", or the letters UN on embossed metal receptacles. It is what tells you this is a specification mark at all.

Two, the identification code

Designating the packaging type, the material and the category, with the letters V or W included where applicable. Type and material together, in a short code.

Three, the performance standard

A single letter, X, Y or Z, identifying which packing group tests the design passed. This is the element that caps what you may carry and it has its own section.

Four, specific gravity or mass

For liquids, the specific gravity tested, rounded down to the first decimal, which may be omitted when it does not exceed 1.2. For solids or inner packagings, the maximum gross mass in kilograms.

Five, test pressure, or a letter

For liquids, the hydrostatic test pressure in kilopascals rounded down to the nearest 10. For solids or inner packagings, the letter S.

Which means one character tells you liquid or solid

An S in position five is a solids packaging. A number is a liquids packaging with a tested pressure. That is a useful glance.

Six, the year

"The last two digits of the year of manufacture." Which matters because reuse and periodic requirements run from it.

Seven, the country

The letters indicating the state authorizing the mark, for example USA. The authorization is national even though the scheme is international.

Eight, the maker

"The name and address or symbol of the manufacturer." Which is what makes the whole mark attributable, the same instinct as the trademark requirement in the jewelry metalwork property.

Nine, thickness where it applies

For reusable drums and jerricans, the material thickness in millimetres. A reuse-related element, present only where reuse is contemplated.

References

49 CFR 178.503(a), marking of UN specification packagings. In sequence: the United Nations symbol "as illustrated in paragraph (e)(1)(i)", or the letters UN on embossed metal receptacles; the packaging identification code designating type, material and category, with the letters V or W where applicable; a letter identifying the performance standard; the specific gravity or mass tested for; the test pressure or the letter S; "The last two digits of the year of manufacture"; the authorizing country, for example USA; "The name and address or symbol of the manufacturer"; and for reusable drums and jerricans the material thickness in millimetres. The example markings at (e)(2) are given as images rather than text. law.cornell.edu

49 CFR 178.503(a)(4) and (a)(5). On specific gravity or mass: "For packagings without inner packagings intended to contain liquids, the designation shall be the specific gravity rounded down to the first decimal but may be omitted when the specific gravity does not exceed 1.2; and... For packagings intended to contain solids or inner packagings, the designation shall be the maximum gross mass in kilograms". On test pressure: "(i) For single and composite packagings intended to contain liquids, the test pressure in kilopascals rounded down to the nearest 10 kPa of the hydrostatic pressure test that the packaging design type has successfully passed; (ii) For packagings intended to contain solids or inner packagings, the letter 'S'". law.cornell.edu

Written from 49 CFR 178.503 and from the catalog as it stood on 19 October 2026. No specimen UN mark appears here, because the regulation gives its examples as images rather than as text. Nothing in this catalog is offered as UN specification packaging: we do not record whether a container carries a mark, and the mark belongs to a tested design type and is applied by its manufacturer. Packing group determinations, shipping names and documentation are the shipper's.