You can find this information printed on the back of your keyboard.
Dell Latitude E6400 E6500 Precisionn M2400 Microphone Board - 0XP558 XP558
English British Keyboard Dell Latitude E6400 E6500 NSK-DB10U 0HT517 507
Dell Latitude E6400,E6400 ATG Control Panel Keyboard Trim
Dell Latitude E6400 Volume Button LED Cover Trim
Dell Latitude E6400 ODD Optical Disk Drive Plastic Faceplate
Dell Latitude E6400 Audio USB Ethernet Board LS-3803P LS-3809P
