Mexico, 1861, 4r black on yellow, half used as 2r, San Luis Potosi. Right half of stamp tied by full San Luis Potosi oval handstamp (Schatzkes 1445) on 1861 folded letter to Zacatecas, with additional cds alongside (Schatzkes 1443), Very Fine; with 2007 Jaretzky and 2010 MEPSI certificates. Scott No. 9a  Estimate $300 - 400. $0 (Image)