Which office should be contacted for filing a trademark petition?

The Petitions Office is the correct point of contact for filing a trademark petition because it is specifically designated to handle various types of petitions related to trademark registrations. This office oversees different procedures such as petitions for reinstatement, petitions to cancel, and other requests that are procedural in nature.

The other offices mentioned, while they have their own specific functions within the USPTO, are not the right contact for general trademark petitions. The Trademark Trial and Appeal Board, for example, primarily deals with appeals from trademark application refusals and opposition proceedings; the Post Registration Division handles maintenance filings for marks that are already registered; and the Madrid Processing Unit focuses on international applications under the Madrid Protocol. Thus, for any type of trademark petition, the Petitions Office is the appropriate office to contact.