Fulgencio Yegros with C overprint, 2,50 pesos yellow brown on registered letter (with content, signed expedition paper, written Dolderia Maca-Indianer Chaco, Kilometer 783 and picture) from explorer Otto Wili Ulrich to mr. Walter Blank New York, received New York 20.1.1932, by runner from Chaco to Rio Confuso, Pony express to kilometer 400, canoe to Rio Paraguay, bull cart to Monte Sociedad and by paddle steamer to Asuncion, very interesting