I've always thought he usual UFP emblem looks too much like the United Nations/United Earth emblem. So I preferred to use the UFP pennant on all my ship designs. The pennant then worked its way onto all the Vanguard book covers. Yay!
By the way, this ship was (according to my fictional history), built by the United Earth during the Earth-Romulan War and then became a part of the new Starfleet in 2161.