What Do the Numbers on My Key Mean?
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
The Anatomy of a Key
To understand the numbers and letters, you need to know the different parts that make up a key.
- Bow/head: The bow works as the handle you use to hold and turn the key. Most key numbers appear here.
- 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.
- Blade: The blade is the business end of the key and is where the cuts that correspond to the key's bitting are located.
- 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."
- 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.
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.
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.
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.
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:
- Original manufacturer
- 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.
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.
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.
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.
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