Standardised numbering and identification system for intermodal shipping containers

You can learn alot about any seacan by checking the serial number.  All shipping containers used in intermodal freight systems have unique identifiers and the standard is managed by the International Container Bureau (BIC).

The standard called ISO 6346 is an international standard covering the coding, identification and marking of all intermodal shipping containers used within containerized intermodal freight transport systems worldwide.  The standard identifies the unique serial number, check digit, the owner, country, size, type and equipment category.

Owner code

Using the above example the owner code is CBH. The owner code consists of three capital letters of the Latin alphabet to indicate the owner or principal operator of the container. Such code needs to be registered at the Bureau International des Conteneurs in Paris to ensure uniqueness worldwide. So if you go to the lookup page for BIC codes you see CBH is

But not all containers are in the register if you take this example:
 
If you lookup FWC (remember the U is the category identifier) you will find no result in the registry.  That is simply because this container was built for selling the container and is not registered under the intermodal container system.

Category Identifier

The U is the category identifier.

The equipment category identifier consists of one of the following capital letters of the Latin alphabet.

• U for all freight containers
• J for detachable freight container-related equipment
• Z for trailers and chassis

Under the ISO code, then, only U, J, and Z are in use—the reefer container is identified by means of the size type code.

Serial Number

The serial number consists of 6 numeric digits, assigned by the owner or operator, uniquely identifying the container within that owner/operator's fleet.

Check Digit

The check digit consists of one numeric digit providing a means of validating the recording and transmission accuracy of the owner code and serial number.
To lookup a check digit go here: bic code

Container Type Code

The size / type codes above are the 4 digits below in this case: 22G1 and 45G1.  So let's see what this means.

The following is an overview of the most common codes taken from Wikipedia.

So as you see below 22G1 is a "General Purpose Container"

45G1 indicates a "High Cube container"