What Do the Numbers on My Key Mean?

Updated on November 29, 2017
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The Four Categories of Key Numbers

Keys have all kinds of numbers, letters, and symbols on their heads. Some are stamped into the metal, while others are embossed during the molding process. I've provided this guide to describe the information contained in the letters and numbers.

The numbers chiefly fall into the following four categories:

  • Bitting Numbers
  • Key Blank Model Numbers
  • Key Numbers Within a Master Key System
  • Key Code Numbers

FIGURE 1
FIGURE 1 | Source

The Anatomy of a Key

To understand the numbers and letters, you need to know the different parts that make up a key.

  1. Bow/head: The bow works as the handle you use to hold and turn the key. Most key numbers appear here.
  2. Stop: Located next to the bow on most keys, the stop keeps the key from going too far into the lock. Distances are measured starting at the stop to locate the cuts. On certain types of keys, the stop is located at the tip (end) of the key rather than the bow.
  3. Blade: The blade is the business end of the key and is where the cuts that correspond to the key's bitting are located.
  4. Cuts: In order to make a standard pin tumbler key, you need to cut material away to specific depths to accommodate the length. These depths are numbered according to their size in thousandths of an inch. For example, a number one (1) cut may be .213" (two hundred thirteen thousandths of an inch) on a particular key brand. Listed, these depth numbers comprise the bitting of the key. If a key has no cuts, it is not called a key. It is called a "blank."
  5. Tip: You can find the tip at the opposite end of the key from the bow. It's used to identify the order of a bitting. For example, you could say the bitting on this key is written "bow to tip".

The illustration above shows the different components of a key.

FIGURE 2
FIGURE 2

What Are Bitting Numbers?

Here are two examples of bitting numbers stamped on keys.

In the photo above, we see a close up of the head with a five-digit number towards the bottom. This number is the bitting. If we look at these digits one at a time and then look at the blade of the key in the reference photo, we see that the first cut (starting from the bow end) is a number "2" and not so deep. The second cut, a number "6," is significantly deeper. If we compare the cuts to their corresponding numbers in the bitting, we can see that the larger the number, the deeper the cut. This is typically the way bittings are constructed. By comparing the numbers to the cuts, we can tell that the number stamped in this key is, in fact, the bitting.

FIGURE 3 - The Keyway of a Key
FIGURE 3 - The Keyway of a Key

The Keyway of a Key

In this case, the stop shows the letter "C". On many Schlage keys, this is where the keyway of the key is shown. The keyway is the shape of the key when viewed from the tip and determines whether or not the key will be able to enter the keyhole of the lock. You can see this in Figure 3 (above).

Bitting numbers can come in a number of formats. Yale Locks, for instance, places an "A" before their bitting numbers to differentiate them from key code numbers. A 6-pin bitting number stamped into the bow of a Yale original key would look like this: A298837.

Figure 3a - Is This Key an Imitation or an Original?
Figure 3a - Is This Key an Imitation or an Original?

How to Know If a Key is an Imitation

In Figure 3a (above), we have what appears to be another Schlage C keyway key with a bitting number on it. Because it does not show a manufacturer's name, however, we can't assume it is a Schlage original. We can see by close examination that the numbers seem to match the depths of the cuts, but we would need to measure them to see if the cut depths are the same as those on a manufacturer's original.

You can use a micrometer to compare cuts on an imitation key with cuts on an original key. If you find a discrepancy of more than two or three-thousandths of an inch (.003 inches), then it is likely the key is an imitation. If it is an imitation, the bitting is useful only to the factory that made the key in the first place.

FIGURE 4 - A Schlage Key
FIGURE 4 - A Schlage Key

Using Bitting Information

In Figure 4, we flipped the key over and the manufacturer's name is prominently displayed. We know the name on the key is the manufacturer of both the key and the lock.

The information we have so far is:

  1. Original manufacturer
  2. Keyway
  3. Bitting number

With these three pieces of information, a locksmith can cut a key for you. If you request a Schlage key with a "C" keyway and bitting number of 26495, the locksmith can make this for you. They can even key another lock to work with the same key. Even more amazingly, the locksmith can do both things without ever having seen or touched the original key. Magical, isn't it?

On the other hand, if the locksmith didn't know the original manufacturer, as with the key in Figure 3a, it's quite likely that the keys made or locks keyed using that bitting would not work properly.

Figure 5:  A Key Blank
Figure 5: A Key Blank

Key Blank Model Numbers

Key blank model numbers appear on the bows of aftermarket blanks. They're used by key duplicators to make copies of keys. When you go to a hardware store or to a locksmith to get a key cut, they copy your key onto a key blank by making cuts in the blank that match the cuts on your key. They can't use any key blank because it must have the same keyway and length.

For keys that fit pin tumbler locks, the key length is described in terms of the number of pin tumblers in the lock that they are designed to operate. For example, Schlage C keyway key blanks are available in 5- and 6-pin lengths.

The blank in Figure 5 (above) was made by the Ilco company, a major manufacturer of key blanks. Notice it has two model numbers. The first number, L1054B, is Ilco's traditional key blank number for this particular blank. The second number, IN8, is probably an Ilco "EZ" number - a system of numbers used primarily for more common key blanks.

Numbers used by key blank manufacturers should not be confused with part numbers used by original manufacturers. The manufacturer's part numbers are usually quite different. For example, the Ilco number for the 5-pin Schlage C keyway blank is 1145, whereas Schlage's part number is 35-100C. ESP, another key blank manufacturer, would call it an SC1 key blank, and this is the Ilco EZ number as well. This shows us that several numbers can be used to identify any given key blank.

Nevertheless, if you can determine the manufacturer of the key blank and the part number used by that manufacturer, you should have enough information for a locksmith to identify the blank you need to cut the key or change the lock. From that information, the locksmith can tell what keyway you have and how many pins are in your lock.

Figure 7 - A Key in a Master Key System
Figure 7 - A Key in a Master Key System

Key Numbers in a Master Key System

Traditional key numbering within a master key system goes like this:

  • The Master Key is key number "A"
  • Sub-master keys are numbered "AA", "AB", "AC," etc.
  • Operating (or pass) keys under each sub-master will be numbered "1AA", "2AA" etc. under the AA sub-master, "1AB", "2AB" and so on under the AB master.

So, when you see a key with a number ending with a letter or two, this probably means it is a passkey in a master key system (see Figure 7 above).

In a master key system, key bittings are designed so every key only opens the door or doors it is intended to open. Therefore, every key is planned and recorded. If the master key system is administered well and you can find who administrates it, you can find out what lock or locks a key operates.

What do you think "1C" means, there on the head? I bet it's the keyway.

Figure 8 - A Key With Code Numbers
Figure 8 - A Key With Code Numbers

Code Numbers

Code numbers are generally found on keys for cabinets, alarm boxes, office and industrial equipment, bike locks, padlocks, and other locks not found on pedestrian doors. Like a master key system, keys with code numbers are recorded and administered. Theoretically, if you lost the key but kept the number, you would be able to get a new key cut.

However, there are published and non-published key codes. Some code numbers are published in books for locksmith use. Some aren't published in those books, so you can't get them from a locksmith. Keys with unpublished codes can only be obtained from the manufacturer with written authorization from the owner of the key, as noted in the manufacturer's records.

Notice the key in Figure 8 (above) has a code with a letter and a few numbers. The format is similar to that of a key in a master key system, and you could think that it is such a key if you didn't know better. The size and key configuration indicate to the locksmith that this is a key by code and not in a master key system. In this example, the size and cut prove this key is not a key in a master key system. Therefore, the number is a code number.

Beyond Key Numbers

You can often find other letters and symbols stamped on key bows. Most locksmith shops, maintenance stores, and real estate offices are equipped with a set of 1/8" letter and number stamps. Many times, people will stamp "MASTER" on the head of the master key for a building for easy reference and fail to consider the security problems that can result. You can also see the ubiquitous "DO NOT DUPLICATE" message coupled with the name and number of your local trusted locksmith.

A bitting conveys the distances measured in thousandths of an inch. Key codes and key number in a master key system point to a bitting number recorded within an organization. Key blank numbers reveal shapes. Key numbers help us visualize the simple and complex functions of the commonplace key.

Figure 6 - An Arrow Lock Company Original Key Blank
Figure 6 - An Arrow Lock Company Original Key Blank
Figure 6a - An Arrow Lock Company Original Key Blank
Figure 6a - An Arrow Lock Company Original Key Blank

A Question to Unlock

Figures 6 and 6a (above) show an Arrow Lock Company original key blank. Can you guess the keyway from the bow markings?

© 2013 Tom Rubenoff

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    • profile image

      Antoinette Spencer 7 weeks ago

      I have a small key silver it has the numbers 555 on it I'm really curious about what this key means and what it belongs to

    • profile image

      Curtis 2 months ago

      I work for a Assisted living facility, I have keys marked 1AA through 101AA. I have duplicate keys that someone cut. I'm missing some keys and instead if trying all the keys I was wondering if there is a list of the cuts so I can check the number against the cylinder. IE. I have cylinder 46AA with no key.

    • Tom Rubenoff profile image
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      Tom Rubenoff 3 years ago from United States

      I will actually write a separate article on that subject, but in short, numbers on locks and keys might be code numbers that may enable a person to cut a key based on that number if (1) the key code is a published code, that is, available in commercially available key code books, or the manufacture keeps the code on file and will translate the code; and (2) the person doing the key cutting is equipped for and skilled in cutting keys by code.

    • profile image

      David Mathibe 3 years ago

      Can you explain the numbers and letters on a padlock can determine a working key if lost your keys.

    • Tom Rubenoff profile image
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      Tom Rubenoff 4 years ago from United States

      I am glad you enjoyed!

    • profile image

      rcorcutt 4 years ago

      This article was awesome. I use a lot of keys at my work and I have always had this almost nerdy curiosity about what the numbers mean but I never looked it up. Thanks.

    • Tom Rubenoff profile image
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      Tom Rubenoff 4 years ago from United States

      Thanks, FlourishAnyway. I have found the interaction between keys and locks interesting for a long time. The numbers and letters stamped on keys and the meanings of those characters is as complex as the evolution of the key. Thanks again.

    • FlourishAnyway profile image

      FlourishAnyway 4 years ago from USA

      I've noticed the numbers before but never thought a whole lot about it. Who knew? Thanks for tell us this information. I find it intriguing.

    • epbooks profile image

      Elizabeth Parker 4 years ago from Las Vegas, NV

      My pleasure!

    • Tom Rubenoff profile image
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      Tom Rubenoff 4 years ago from United States

      There is no higher praise than to learn that one's writing has been of use. Thank you, Epbooks!

      Livewirez, all keys are unique, and so every duplicate is just a little off. The difference of the copy from the original is what determines how well (or badly) it operates the lock. People who duplicate keys generally use a key machine that "reads" the information from the key and simultaneously transfers that information to a cutting wheel that makes the cuts. But it is also possible to duplicate a key using a simple flat file.

      Hmm. I feel another hub coming on. Thank you!

    • livewirez profile image

      Romel Tarroza 4 years ago from Pearl of the Orient Sea

      Nice Hub.. I know that keys are very unique but I am just curious how does those people who duplicate keys can make keys exactly the same as the original?

    • epbooks profile image

      Elizabeth Parker 4 years ago from Las Vegas, NV

      One thing I can honestly say that I never looked at other than its color was a key. I use them every day, but never even noticed there were numbers on them. This is good to know in case I need to get some keys made, which, as a matter of fact, I do!

    • Tom Rubenoff profile image
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      Tom Rubenoff 4 years ago from United States

      Thank you, Storyteller. It does seem that there is often a key to something that figures prominently in mysteries and detective stories; and there are all the key metaphors, too. Thank you!

    • Storytellersrus profile image

      Barbara 4 years ago from Stepping past clutter

      Fascinating information- great material for a book or poem of intrigue!!!

    • Tom Rubenoff profile image
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      Tom Rubenoff 4 years ago from United States

      Glad you liked it and thanks for reading! It is the kind of information that is occasionally very nice to have. Thanks again.

    • tastiger04 profile image

      tastiger04 4 years ago

      Interesting! I've always noticed the numbers on my keys, but never knew what the deal was....thanks for the good read! Voted up and interesting :)

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