Which process involves checking if a trademark has been assigned?

The correct choice is grounded in the specific function of the Assignment Recordation Branch at the United States Patent and Trademark Office (USPTO). This office maintains a comprehensive database of trademark assignments, which includes records that document the transfer of ownership of trademarks from one entity to another. By searching these records, an individual or organization can verify if a trademark has been officially assigned, which is critical for confirming the current owner and ensuring a clear chain of title.

This process is distinct because while reviewing legal documentation or filing security interests might provide related information, they do not specifically focus on the formal assignment of trademark ownership. Searching for filing fees pertains to the cost associated with trademark applications and maintenance, which is unrelated to the ownership status of a trademark. Therefore, accessing the Assignment Recordation Branch's records is the direct method to ascertain whether a trademark has been assigned, making it the most appropriate answer.