Very scarce use of the world's first postage stamp Penny Black used on first day of valid use, May 6, 1840, tied by red Maltese Cross cancel on folded cover to Warwickshire, brown "C MY-6 1840" first day datestamp on backflap verifies date of use. Sold as lot 1018 at Robert Siegal 2006 Rarities of the World auction for $45,000.