Getting started

What the mark is for

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A design type is tested Not each individual container So the mark is a claim about a specification Which is why closures are part of it And why reused packaging is a question The nine elements each encode a limit Which makes the mark readable That is the useful skill this property teaches It does not teach you to apply one And it does not classify your material References

The packaging was tested, not inspected. That distinction is the whole system.

A design type is tested

A packaging design is subjected to a programme of tests, and a design that passes may be marked. The mark records what it passed.

Not each individual container

Which is how the system scales. The individual drum in front of you carries the mark because it is of a design type that was tested, not because it was.

So the mark is a claim about a specification

Make it from these materials, to these dimensions, with this closure, and it performs as tested. Deviate and the mark no longer describes what you have.

Which is why closures are part of it

A tested design includes its closure. A compliant drum fitted with a different cap is not the assembly that passed, whatever the drum is stamped with.

And why reused packaging is a question

The mark stays on the container after its first trip. Whether it may be reused, and under what conditions, is a separate body of rules this property does not address.

The nine elements each encode a limit

Material and type, performance standard, density or mass, pressure, and the maker. Read together they tell you what the packaging may carry.

Which makes the mark readable

Not a serial number and not branding. A trained reader can tell from the stamp whether a container may hold what they are about to put in it.

That is the useful skill this property teaches

How to read it, what each position means, and which element caps what you may carry.

It does not teach you to apply one

Marking a packaging is the manufacturer's act and it follows from testing. Nothing here should be read as describing how to mark anything.

And it does not classify your material

Which packing group a substance falls in, and therefore which letter you need, is the shipper's determination against the hazardous materials table.

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)(3), the letter identifying the performance standard under which the packaging design type has been successfully tested: "(i) X--for packagings meeting Packing Group I, II and III tests; (ii) Y--for packagings meeting Packing Group II and III tests; or (iii) Z--for packagings only meeting Packing Group III tests". 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.