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(Philately) philately chiefly US denoting stamps where all or part of the receipts from sale are given to some charitable cause
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
sem•i•post•al(ˌsɛm iˈpoʊs tl, ˌsɛm aɪ-)
a postage stamp sold above its face value, the excess being used for a nonpostal purpose.
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