What Do The Numbers On My Key Mean?

Types of Numbers on Keys

All kinds of numbers, letters and symbols appear on the heads of keys. Some are stamped into the metal while others are embossed during the molding process. This article is about the information contained in these numbers and letters and chiefly deals with the following categories:

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

Anatomy of a Key

In order to get a basic understanding of numbers and letters that appear on keys it is necessary to know the parts that make up a key. Below is an illustrating showing the various regions and what they are called:

  1. Bow (or Head) - serves as the handle that one uses to grasp and turn the key. Here is where most key numbers appear.
  2. Stop - on most keys located next to the bow, it keeps the key from going into the lock too far. Distances measured starting at the stop locate the cuts of the key. On certain kinds of keys the stop is located at the tip of the key instead of the bow, but it serves the same purposes.
  3. Blade - the business end of the key. Here is where the cuts that correspond to the key's bitting are located.
  4. Cuts - to make a standard pin tumbler key, one cuts away material to specific depths to accommodate the length of a pin. 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 brand of key. Listed, these depth numbers comprise the bitting of the key. See the section about bitting later in this article.
  5. Tip - the opposite end of the key from the bow. Used to identify the order of a bitting. For example, one could say the bitting on this key is written "bow to tip".

If a key has no cuts, it is not called a key. It is called a "blank."

FIGURE 1 | Source
FIGURE 3 - Keyway
FIGURE 3 - Keyway
Figure 3a
Figure 3a

Bitting Numbers

Here are two examples of bitting numbers stamped on keys.

In the photo above we see a close up of the head the key we examined in Figure 1. Toward the bottom of the head we see a five-digit number. 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 Figure 1, we see that the first cut (starting from the bow end) is a number "2" and is not so deep, whereas the second cut, a number "6" is significantly deeper. As we compare the cuts to their corresponding numbers shown in the bitting, we see that the larger the number, the deeper the cut. This is the way bittings are usually constructed, and by comparing the numbers to the cuts we can tell that the number stamped in this key is, in fact, the bitting.

Appearing on the stop is the letter "C". On many Schlage keys this where they show the keyway of the key. The keyway is the shape of the key when viewed from the tip as shown in Figure 3. The shape of the key determines whether or not it will be able to enter the keyhole of the lock.

Now in Figure 3a we have what appears to be another Schlage C keyway key with a bitting number on it, but because it does not have a manufacturer's name on it we cannot assume that it is a Schlage original key. We can see by looking closely at the key that the numbers seem to match the depths of the cuts, but we have no way of knowing whether the depths of these cuts are the same as those on a manufacturer's original unless we measure them.

To compare cuts on an imitation original to cuts on a real original key, one could measure cuts with the same number designation on each key using a micrometer. If there is a discrepency of more than two or three thousandths of an inch (.003 inches) then it is likely the original is an imitation. If it is an imitation, the bitting is useful only to the factory that made the key in the first place.

There are a few formats of bitting numbers out there. Yale Locks, for example, 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.


Using Bitting Information

In Figure 4 at right we have flipped the key in Figure 2 over and, lucky for us, the name is displayed, and even luckier, we know that the name displayed is the manufacturer of both key and lock. Knowing these three things ...

  1. Original Manufacturer
  2. Keyway
  3. Bitting

... a locksmith can cut a key. If you can tell a locksmith you have a Schlage key with a "C" keyway and the bitting is 26495, the locksmith could cut you a key based on that information. What's more, the locksmith could key another lock to work with this same key. Even more amazingly, the locksmith could do both without ever having seen or touched the original key. Magic, eh?

If on the other hand the locksmith did not know the original manufacturer, as with the key in Figure 3a, it is quite possible that keys made or locks keyed using that bitting would not work properly.

Figure 5:  Key Blank
Figure 5: Key Blank
Figure 6
Figure 6
Figure 6a
Figure 6a

Key Blank Model Numbers

Key blank model numbers appear on the bows of aftermarket key blanks used by key duplicators to make copies of keys. When you go into 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 cannot use just any key blank; they must use a key blank of the same keyway and length.

For keys that fit pin tumbler locks, 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 was made by the Ilco company, a major manufacturer of key blanks. Notice that 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 number used primarily for more common key blanks.

Numbers used by key blank manufacturers are not to be confused with part numbers used by original manufacturers, because usually the manufacturer's part numbers are 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 ascertain the manufacturer of the key blank and the part number used by that manufacturer, this should be sufficient information for a locksmith to identify the blank needed to cut your key or change your lock. From that information the locksmith can tell what keyway you have and how many pins are in your lock.

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

Figure 7
Figure 7

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 will be 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, etc.

Therefore when you see a key with a number (as in Figure 7 at right) ending with a letter or two this probably means it is a passkey in a master key system.

In a master key system key bittings are designed so that every key will only open 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 this key operates.

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

Figure 8
Figure 8

Code Numbers

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

However there are published key codes and there are non-published key codes. Some key code numbers are published in key code books for use by locksmiths. Other key codes are not published in these books and you cannot 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 in Figure 8 that the key shown has a code with a letter and a couple of numbers. This is similar to the format of a key in a master key system, and indeed one could think that it is such a key if one did not know better. Clues for the locksmith that this is a key by code and not a key in a master key system is the size and configuration of the key. Because of its size and the way it is cut, this key is plainly not a key in any normal master key system. Therefore the number must be a code number.


There are often other letters and symbols stamped on the bows of keys. Most locksmith shops and many maintenance and real estate offices are equipped with a set of 1/8-inch letter and number stamps. Many times the less thoughtful will stamp "MASTER" on the head of the master key for a building thinking only of their own convenience, not of the increased potential for a security problem resulting from this label. In addition there is the ubiquitous "DO NOT DUPLICATE" and the often encountered name and telephone number of your local trusted locksmith.

The deeper aspect is meaning. A bitting symbolizes distances measured in thousandths of an inch. A key number in a master key system symbolizes a bitting number recorded somewhere within some organization, as do key code numbers. Key blank numbers symbolize shapes.

Symbolization is a means of visualizing reality. Key numbers help us visualize the simple form yet complex function of that everyday, everywhere object: the key.

© 2013 Tom Rubenoff

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Comments 14 comments

tastiger04 profile image

tastiger04 3 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 :)

Tom Rubenoff profile image

Tom Rubenoff 3 years ago from United States Author

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

Storytellersrus profile image

Storytellersrus 3 years ago from Stepping past clutter

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

Tom Rubenoff profile image

Tom Rubenoff 3 years ago from United States Author

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!

epbooks profile image

epbooks 3 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!

livewirez profile image

livewirez 3 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?

Tom Rubenoff profile image

Tom Rubenoff 3 years ago from United States Author

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!

epbooks profile image

epbooks 3 years ago from Las Vegas, NV

My pleasure!

FlourishAnyway profile image

FlourishAnyway 3 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.

Tom Rubenoff profile image

Tom Rubenoff 3 years ago from United States Author

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.

rcorcutt 3 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

Tom Rubenoff 3 years ago from United States Author

I am glad you enjoyed!

David Mathibe 2 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

Tom Rubenoff 2 years ago from United States Author

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.

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