A Ford Motor Company part's number indicates the year of manufacture, the intended body type and the relevant design engineering office. It also has a portion specific to the part and its application. It generally contains a suffix that indicates the number of times that part has undergone change.
The prefix indicates the year of manufacture, the model and the source for the part. The first letter in the series is the decade, beginning with A for the 1940s, B for the 1950s, and so on. The second character shows the year inside the decade. So if the part starts B6, it was made in 1956. The third character indicates the product part that the replacement was designed for, and the fourth character indicates the source of the part, either engineering office or service part.
In the example B6ZZ-6366-F, the manufacture date (1956) is already known. The Z in the prefix indicates a Ford Mustang between 1964 and the present day. The second Z in the prefix indicates that the part is from Ford Service Parts. After the prefix, moving to the next set of digits reveals the type of car. This example numbered part serves an owner of a two-door hardtop, such as the Mustang Fastback. The suffix, F, indicates the part is on its sixth level of modification. At this point, some variety enters the interpretation of the codes, as different combinations of letters indicate the part's color or finish, as well as whether the user needs to be right-handed or left-handed.