That piece is not the antenna per se. The actual antenna is formed by two pieces of the case, isolated from the rest by some plastic strips:
Here is the piece installed in a phone, image from ifixit.com:
You can see two of these screws attach to the section on the top of the phone, while others attach to the section surrounding the camera.
Inside the part itself is likely a matching network. Similar parts contain a chip capacitor under the black covering, and the two arms bent at 90 degrees may be a transmission line. The black covering is likely to avoid shorts to the case and other components.
https://www.ifixit.com/Answers/View/223445/iPhone+6+cellular+antenna+location-replacement#answer223453 claims this is only the “antenna upper bus bar assembly” which connects the case (acting as the actual antenna) to the circuit. Which would also explain the six connectors.