What is indicated by the letter U or X in the beginning of a serial number?
Some Bendix/King avionics units have the letter U or X in the beginning of the serial number (e.g. X87544). Units with the letter X indicate that the unit is in like new condition and has been cosmetically enhanced. In most cases, faceplates and covers have been replaced by Honeywell so that the unit appears the same as a new unit would. In addition, the letter X indicates that the product is less than 3 years old, has the latest software and hardware mods installed, and was repaired by the factory or the factory repair and overhaul shop. Units with the letter U indicate that the unit in average physical condition and, in most cases, have not had much cosmetic enhancement done at the factory. These units are usually more than 3 years old but do have the latest software and hardware mods installed while being repaired at the factory.
