Locations of type LOCALITY can be associated with zero, one or more postal codes. To distinguish between localities with the same name but in different regions, a representative postal code is returned in the postal code field of the locality. This representative postal code consists of the common leading characters of the associated postal codes, with asterisks indicating where they differ.
Other types of location like STREET, POSTAL_CODE, EXACT_ADDRESS, etc. may or may not have a postal code assigned. However, if a postal code is assigned, it is always exact and not representative.
A representative postal code cannot be used as an input for a location search. For this reason the suggestion search endpoints will never return a representative postal code.
Example
A location search with 'Karlsruhe' as the input may return the locality 'Karlsruhe' with the postal code '76***' as a result. This is because the city of Karlsruhe is divided into several postal code areas, such as 76131, 76135 and 76229, which are combined to the representative postal code '76***'.
Another example would be a search for 'Oxford' which will return 'OX***' as a representative postal code for this area in GB.