Unlocking the Secrets of Cat Equipment Codes. What All Those Letters Mean


Caterpillar Inc. is an American corporation that designs, develops, engineers, manufactures, markets, and sells machinery, engines, financial products, and insurance to customers around the world. It is a global leader in the heavy equipment industry, with a strong heritage and history dating back to the early 1900s.

One of the unique aspects of Caterpillar equipment is the lettering and numbering system used to identify each machine. Caterpillar has used a standardized system of letters and numbers since the early days of the company to designate model types, model years, serial numbers, and manufacturing locations. These codes are important for owners, operators, dealers, and collectors to understand the history and specifications of a piece of Cat equipment.

History of Lettering on Cat Equipment

The lettering system for Caterpillar equipment dates back to the 1920s when Caterpillar started using serial numbers to identify their machines. According to The Evolving Look of Cat® Machines, in the 1920s and 30s, Caterpillar used a mix of serial numbers and model numbers like “Model 25 – Serial Number 10001” painted on the sides of their equipment.

It wasn’t until the 1950s that Caterpillar started using distinct letter codes to designate different equipment types, like “D” for dozers and “980” for large wheel loaders. Over the decades, the lettering schemes have evolved to include more specific model designations as Caterpillar expanded its product lineup.

According to Caterpillar’s company history timeline, in 1973 Caterpillar officially adopted the “CAT” brand name and the stylized CAT logo that appears on modern machines. So older equipment will only have “Caterpillar” lettering without the CAT brand.

Today, the lettering sequence combines equipment type letters, model numbers, and serial numbers into computerized schemes that can precisely identify the machine’s configuration and manufacture details.

Equipment Type Letter Codes

For many years, Caterpillar used letter codes in their model numbers to identify the type of machine. This helped differentiate between similar machines in the product line. Some common letter codes include:

D – Dozers Caterpillar Dozer Nomenclature

B – Backhoe Loaders

E – Excavators

W – Wheel Loaders

M – Motor Graders

P – Pipelayers

R – Skid Steer Loaders

S – Scrapers

T – Track-Type Tractors

These letter codes helped customers identify the type of Caterpillar machine at a glance based on the model number. The codes were an integral part of Caterpillar’s equipment naming conventions for many years.

Serial Number Conventions

Caterpillar serial numbers follow a standard format that provides information about the equipment’s type, year of manufacture, and factory location. The formats have changed over the years as Caterpillar’s product line and manufacturing operations have evolved.

Older Caterpillar machines from the 1930s-1950s used a simple serial number format consisting of a two-digit year code and a four or five digit machine sequence number. For example, a serial number of “481234” indicates the machine was built in 1948 and was the 1234th machine produced that year.

Starting in the 1960s, Caterpillar began using longer 10-digit serial numbers on most equipment. The first two digits indicate the machine type (e.g. “77” for Track-Type Tractors), the next four digits show the year and month of production, and the remaining digits are the machine’s sequence number.

In later years, as Caterpillar grew into a global company with factories around the world, the serial number formats evolved to include factory codes. Modern Caterpillar serial numbers consist of a two-digit machine type code, followed by a one or two-letter factory code, a four-digit year/month code, and finally a six-digit machine sequence number. Decoding the factory codes requires referencing Caterpillar documentation to identify where the equipment was originally built.

Understanding the serial number conventions used by Caterpillar over the decades is the key to decoding the manufacturing details of any Cat machine.

Year of Manufacture Codes

Caterpillar equipment have used several different formats for year of manufacture codes over the years. The codes are found within the serial number sequence and indicate the year the machine was built.

From 1925 to 1972, a letter code was used to represent the year of manufacture. For example, the letter “F” stood for 1965 and “S” represented 1972. This single letter code made it easy to quickly identify the build year.

Starting in 1973, a new numeric system was introduced, with the number 73 indicating models made that year. This two digit number system was used up through 1999 models, with 99 standing for 1999 production.

In the year 2000, Caterpillar switched to a four digit numbering format to avoid any ambiguity with prior codes. So the year 2000 was encoded as 2000 within serial numbers. This four digit year code has continued to present day.

There are some exceptions to the year of manufacture code conventions. Some models built from 1973-1986 continued using the old single letter system rather than the new two digit code. Also, the four digit year started appearing as early as 1988 on some models before becoming universal in 2000.

So in summary, check for either a single letter (1925-1972), two digits (1973-1999 on most models), or four digits (1988-present on newer models) within the serial number to determine the year of manufacture for your Caterpillar equipment.

For more details, see the Caterpillar serial number guide at https://parts.cat.com/en/catcorp/cat-serial-number-identification

Factory Location Codes

Caterpillar equipment has a unique letter code that identifies which factory it was manufactured in. This single letter code is part of the full serial number stamped on the equipment. Each Caterpillar factory location around the world has its own specific letter code.

Some examples of factory location codes include:

  • A – Aurora, Illinois, USA
  • B – Belgium
  • E – England
  • F – East Peoria, Illinois, USA
  • L – France
  • M – Muncie, Indiana, USA
  • P – Pontiac, Illinois, USA
  • S – Sweden

Knowing the factory location code letter in the serial number provides information on where in the world that particular piece of Caterpillar equipment was built. This can be useful for determining replacement parts availability or the equipment’s original destination market.

The factory code letters are consistent, so once you learn where each letter represents, you can quickly decode where any Cat machine originated.

Explanation of Complete Serial Numbers

Caterpillar serial numbers follow a standard format that reveals useful information about the equipment. Here is a breakdown of what each part of the serial number indicates:

The first letter(s) identify the equipment type, such as “A” for traxcavator. The next set of digits indicate the machine’s serial number, which is unique to that individual model. The next letter(s) denote the year of manufacture; for example “A” would mean 2010. The following two letters reveal the manufacturing factory location. Finally, the last four or five digits represent the machine’s product line number.

Putting this all together, a sample serial number might be A123A01FL01234. This would be interpreted as:

  • A – Traxcavator
  • 123 – Unique machine serial number
  • A – Year of manufacture – 2010
  • 01 – Factory location code – East Peoria, IL, USA
  • FL – Product line number

Being able to decipher the meaning behind Caterpillar serial numbers provides valuable information about a machine’s history and specifications.

Special Lettering Schemes

Caterpillar sometimes uses special lettering schemes on certain models or custom/limited equipment. One notable example is the Caterpillar 500 series, which uses a distinct lettering format.

On the 500 series, the serial number begins with “B5N” followed by a 6 digit serial number. So a 500 series machine might have a serial number like B5N123456.

The “B5N” indicates it is part of the 500 series made at the East Peoria factory in the 1980s. The 500 series was unique because it introduced a new easier starting diesel engine designed by Caterpillar.

Custom or limited edition equipment may also have unique serial numbers or special badging to indicate its exclusivity. For example, Caterpillar sometimes produces special “anniversary edition” machines to celebrate milestones. These machines stand out through badging, color schemes, and custom serial numbers indicating the limited production run.

Deciphering Your Cat’s Codes

Interpreting the letters and numbers on Caterpillar equipment can reveal useful information about your machine’s year of manufacture, factory location, and more. Here are some tips for deciphering your Cat’s codes:

Find the machine’s full serial number, which should be prominently displayed on a metal plate attached to the equipment. Caterpillar serial numbers follow a standard format of a letter followed by six digits (e.g. J12345).

The first letter indicates the type of equipment, such as B for backhoe loader or D for dozer. The year of manufacture can be determined from the first number, along with the factory location from the second digit.

There are several handy online resources that provide tables to look up equipment codes based on the serial number:

According to Frictionless Equipment, the website Caterpillar.com lets you enter a full serial number to decode the year, factory, and type of machine.

Additionally, this overview from Frictionless Equipment provides printable quick reference tables matching letters and numbers to different Caterpillar equipment models over the years.

With some basic information about your Cat’s serial number format, and the help of online resources, you can unlock useful insights into your machine’s history and origin.


To recap, Caterpillar has a unique system of lettering and numbering their construction equipment to identify model types, serial numbers, production years, and factory locations. The letters on Cat machines serve important functions in inventory management and parts identification.

By understanding the lettering conventions, owners can decode their equipment’s serial number to determine key details about its manufacturing origin and service history. The codes help connect each individual machine to its record within Caterpillar’s databases.

While Caterpillar is evolving how model names are presented, the serial number lettering system persists as a way to trace each piece’s lifecycle. For over 50 years, the codes have provided a common language for dealerships and customers alike when managing mixed fleets of Cat equipment. They will continue serving their core purpose as an institutional knowledge base for the brand.

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