When a packaging has passed its performance test criteria, markings indicate the performance rating and test information specific to the certification test. This information must be applied in accordance with CFR 178.3(a)(3). For drums over 100 Litres (26 US Gallons) there are a number of ways that the marking can be applied including stamping, embossing, burning and printing and there must be one complete set of durable marks on the side or non-removable top head, and a second partial mark embossed permanently on the bottom head. The purpose of having the two marks is that once filled, the drum will sit, primarily, on its bottom head, and the UN test information will be readily viewable for the user at the side or top mark. The permanent partial bottom mark must conform to the application options indicated earlier. However, the side or top mark is required to be durable rather than permanent. Therefore, it is common and acceptable for the durable mark to be printed on the drum, or on a self adhesive label which is attached to the side of the drum. The characters on the label and the permanent embossment are subject to the size and sequence requirements as specified in 178.3(4) and 178.503(a)(1) through (a)(6) and (a)(9)(i).
Skolnik.com offers a unique breakdown of the individual marks by drum style. Click any of these links to understand the marking code: