Post Office Seal, 1958, experimental adhesive tape. Tape strip used to seal a 1958 legal size cover bearing 4¢ #1117 strip of three tied by "Chicago Ill 1958" double-circle postmarks; two additional off-cover strips accompanies, Very Fine, these two strips are the only recorded examples of this experimental seal. Scott No. OX var.  Estimate $200 - 300. The official seal tapes were only distributed to Chicago and used only briefly. Hank VanLaar, an employee in the Chicago Post Office at the time wrote in 1988, "This tape was an experiment by the POD back in the '60s…I think there were six roles in the box and they were used up in a few weeks". $0 (Image)