1906, 1¢ blue green, imperf, Rosback Coil Pair. privately perforated 12 for the Covel Co. (by Schermack and Rosback), horizontal pair tied by Brinsbane, Cal., Mar18, 1915 duplex postmark on Covel Mfg. Co. printed return cover, Very Fine, a scarce and elusive private coil usage on cover; with 1992 A.P.S. certificate. Scott No. 314 var.  Estimate $400 - 600. $0 (Image)