1906, 1¢ blue green, imperf, Rosback Coil Pair, privately perforated 11.75, for the Covel Co. (by Schermack and Rosback), horizontal pair tied by "Benton Harbor, Mich, Dec 20, 1915" machine postmark on Covel Mfg. Co. printed return cover, Very Fine, a scarce and elusive private coil usage on cover; with 2013 P.F. certificate. Scott No. 314 var.  Estimate $400 - 600. $0 (Image)