Released and stamped with the alternate First Day Issue cancellation mark (available only at the 2007 San Diego Comic Con itself, there were two cancellation marks available... the standard one with Spiderman and this one with the SDCC logo).  The stamp collection itself also debuted at ComiCon).  It is an official USPS stamp and the set features both Namor stamps from the 20 stamp collection. In nm/mint condition, both FDI's will be shipped with the utmost care.