The cédula de identidade is the official national identity document in Brazil. It is often informally called carteira de identidade (identity card), "RG" (from Registro Geral, General Registry)
The card contains the name, birthdate, parents' names, signature and thumbprint of the bearer. Other national documents can legally be used as an identity card, such as a federative unit-issued driver's license, passport or, for minors, a birth certificate. Brazilian identity cards can be used as travel documents to enter the Mercosul countries. Each card has a unique RG number. (wikipedia)
Its issuance is the responsibility of the governments of the federative units of Brazil and are valid nationwide. There is no legal restriction on having more than one identity card, provided each one is issued by a different federative units.
This tool was developed for programmers and testers who have the constant need to enter different RG numbers in developing forms.