AO-B2, 2002, Heroes of 2001, New York City, Add-on Cachet, FDC, 9-11, Firefighters Raising Flag at Ground Zero SC B2

Add-on cachet is:

A cachet design added to a cover which was originally uncacheted. An add-on cachet should be identified

by maker and date (mine are stamped on the back with the date) so that it is clear that it is not contemporary with the cover.