1921 (April 10), cover from Experimental Unsuccessful Flight San Jose - Managua, franked by Mauro Fernandez 5c orange and semi-official air post stamp ''Costa Rica - Nicaragua'' of 1col green and yellow, minor cover folds, still F/VF, Sanabria #501, Est. $250-$300 (Image)

1924 (July 12), Pioneer Flight cover San Jose - Puerto Limon, addressed to Cartagena (Colombia), franked by Main Post Office 5c light blue and Statue of Santamaria of 1c brown in horizontal strip of five bearing inverted (!) red se-tenant semi-official surcharges 8c, 16c, 32c, 32c and 4col, which is not listed either in Scott or Sanabria, Cartagena arrival ds on reverse, F/VF and rare, Est. $250-$300 (Image)

1940, Pan-American Aviation Day, black surcharge 15c on Map of Cocos Island stamp of 25c orange instead of 50c yellow, full OG, NH, VF and scarce, expertized by A. Roig and others, Est. $150-$200 (Image)