I was looking at my keys and noticed something on them, at the hilt of the part that actually goes in the lock there is a single letter stamped. On my Ford F-150 keys (for the ignition and the door lock) the letter H is stamped. On my house key an I is stamped, and on my dorm room key a G is stamped. What are these letters here for?
WAG, they identify the key template.
They mean whatever the stamper meant them to mean. In other words, there is no standard.
Except: Sometimes you’ll see the actual cut codes stamped on a key. For example, a schlage might read 96473, which means that the five cuts on the key are cut to those five depths.
The maker of the keys denotes the letters Most often to identify the keyway grooving.
BEST IC core has quite a few common keyblanks that look similar A,C,D,F
Schlage has both the C and E
These make them easy to identify what is required to rekey or duplicate. They are of course how the original Manufacture IDs their keys.
After factory blanks might also have other numbers to help the locksmith or technician quickly ID what keyway.
This makes a huge difference for me.
I can talk to a customer needing their locks rekeyed to describe their key over the phone so I can insure to have the correct blanks avalibe for the job.
An example: Customers key has the letter C stamped on the the head of the key near the blade and the head of the key is shaped in a step pattern. I know then it is a Schlage 1145C or what is also refered to SC1.
BillH is also correct that an original key will have the cut depths stamped on them, this is found mostly found on residential or commercial hardware.
Automotive original keys do not have this done for the most part. If they do have a code it is not read directly for depth but can be looked up in a code source book or computer program to get the correct depth cuts.
Key codes are great to generate new keys when the originals are lost.
Osip