Given the task definition and input, reply with output. Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.

The Official Municipality Key, formerly also known as the Official Municipality Characteristic Number or Municipality Code Number, is a number sequence for the identification of politically independent municipalities or unincorporated areas.

The Official Municipality Key, (was known as the Official Municipality Characteristic Number), is a number order for the ID of independent cities or unincorporated areas.