Is there any case law in which a jury convicted a defendant of conspiracy with other unknown persons?

Furthermore, although the instant indictment so charged, this was not a case like United States v. Artuso, 618 F.2d 192, 197 (2d Cir.), cert. denied, 449 U.S. 861, 101 S.Ct. 164, 66 L.Ed.2d 77 (1980), where there was evidence from which the jury could rationally have convicted Mamone of conspiracy with "others unknown". Both the district court and the government apparently recognized this, for Count One was not submitted to the jury on the "others unknown" theory, and the government did not except to the charge as given.