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:
- Bow (or Head) - serves as the handle that one uses to grasp and turn the key. Here is where most key numbers appear.
- 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.
- Blade - the business end of the key. Here is where the cuts that correspond to the key's bitting are located.
- 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.
- 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."
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 ...
- Original Manufacturer
... 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.
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?
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.
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