The container identification system is an ISO standard (ISO 6346) composed of a sequence of letters and numbers. The above photo, this identification is displayed on the top right part of the container:
- Owner code. Consisting of three capital letters that identify the owner of the container. There is an international agency (Bureau International des Containers et du Transport Intermodal) that issues owner codes on behalf of ISO so that no single code is assigned to more than one owner. In the above case, the container belongs to the American company Textainer, the world’s largest container leasing company with a fleet of 3.5 million units. For the purpose of brand identity, shipping and container leasing companies usually advertise their logo on the container, which is often painted with distinct colors.
- Product group code. Appears right after the owner code and consists of one capital letter, either U, J or Z; U refers to a container, J refers to equipment that can be attached to a container, such as a power unit and Z refers to a trailer or chassis used to carry a container. Therefore, each mobile intermodal equipment has its own identification code.
- Registration Number (or Serial Number). A sequence of 6 digits where each container belonging to an owner has a unique value. Therefore, each owner code can have up to 1 million containers.
- Check digit. This single digit is used to cross-verify if the identification sequence is accurate. By convention, it is boxed to make sure it is separated and is standing out from the registration number. Since terminal gates handle a large number of containers, there is always a risk that the identification sequence was not correctly inputted. The standard procedure involves the sequence to be remotely inputted by a video camera with the operator entering the sequence manually in the information system. Increasingly, that sequence being inputted automatically through optical character recognition software. A numerical operation is performed on the container identification sequence (owner code, product group code, and registration number) which results in a single-digit number, which is then compared with the check digit. If they match, then the identification sequence is accurate (there is still a probability for error, but it is very low).
- Size and type code. A sequence of 4 letters or digits that commonly appear right under the container identification sequence. Its purpose is to provide information about the dimensions and the type of container; the first character is related to the length of the container while the second character is relative to its height. On the above photo, the first two numbers 45 indicate that the container is a 40 footer (4; commonly the length of the container) of 9 feet 6 inches in height (5; high cube). The remaining two elements of the sequence (G1) indicate that it is a general-purpose container.
The operational characteristics of the container are also commonly displayed. They include the maximum gross weight which is the maximal weight the loaded container can have, which is commonly around 30 metric tons. The container weight (Tare) is also provided, a number which should be between 4 to 10 metric tons. The payload is simply the gross minus the tare weight, which is the maximum weight that can be loaded into the container. Maximum cargo volume information is also provided since cargo carried by container tends to “cube out” before it “weights out”.