None, they represent the same unit. Original King Radio part numbers were 9 digits. For example, 066-3056-01. During the Bendix and King merger (i.e. Bendix/King), a new part numbering system was created that converted these 9 digit part numbers to 12 digits. Therefore, 066-3056-01 became 066-03056-0001. Despite this numbering change, units that were originally from the King Radio design still have the 9 digit part number format on the unit dataplate. The 12 digit format for King units appears to be used for catalog and internal Honeywell purposes only. Therefore, any unit that has a zero in its third to last number (i.e. XXX-XXXX-X0XX) has a 9 digit part number (i.e. XXX-XXXX-XXX) on its dataplate / ID Plate.

In January 1989 Bendix/King changed from a nine digit to a twelve digit part numbering system. The new, larger 12 digit numbers allowed for the inclusion of software version into the last two digits of the part number for certain units in which software changed frequently such as EFIS and TCAS processors. Therefore, the two digits immediately preceding the software version indicate the hardware version of the unit.

Different software versions imply different operational features and/or interface capabilities and software modifications imply software repairs (bug fixes) to insure proper operation of these features and interfaces. Software version upgrades frequently require hardware modifications to the unit. Such hardware modifications accompanying software version upgrades do not necessarily change the hardware version of the unit.

Negotiating the exchange price of a unit only limits the allowable repair cap for the core unit. Southeast Aerospace's exchange transactions are based on the return of economically repairable core unit. Once the core is received and evaluated, the core repair cost incurred by SEA cannot exceed 75% of the original exchange price. That is, it cannot cost SEA more than 75% of the original OH/SV exchange price collected from the customer. Therefore, when and if an SEA exchange price is discounted, there is a risk that additional charges may be assessed once the core is returned and evaluated.

For more information, please refer to these other Exchange FAQs