UL File Number
A UL File Number identifies the manufacturer of a component or product, as found in the database of UL (formerly Underwriters Laboratories).
These take the form of the letter "E" plus a number of digits, typically six. These "E numbers" are used both as PCB inscriptions that can be used to identify the manufacturer of PCBs in keyboards, as well as on the rear label identifying the OEM of the keyboard as a whole.
Not all E numbers are on file. Microsoft peripherals use E145346 and Logitech use (or at least did use) E97600, both of which are unlisted.
Some file numbers of common manufacturers:
|E134780||Primax Electronics||Dell KB1421, Dell KB212, Cherry G82-27000|
|E141395||Sunrex Technology||Cherry eVolution STREAM XT|
|E206453||Darfon Electronics||Dell L100|