Post Office Seal, 1907, bright royal blue, imperforate with "Supposed Liable to Customs Duty" overprint. Bottom margin pair with essay overprint, large margins, unused, Very Fine and unusual. Scott No. OX12 var.  Estimate $200 - 300. These seals should be considered essays. The post office was apparently experimenting with printing seals directly onto the custom seals. Seals were often used to reclose mail opened for customs inspection. $0 (Image)