522 F.3d 105, 110 (151 Cir. 2008) ("A return of service generally serves as prima fade evidence that service was validly performed."); Gottlieb v. Sandia Am. Corp., 452 F.2d 510, 514 n. 5 (3rd Cir.1971) ("although a marshal's return is not conclusive on the question of service on an agent, it will stand in the