CH 2001 Stamp Day Basel BS, cover cancelled UN-5.3.2002 United Nations New York (UNO NY)

Switzerland 2001 Stamp Day Basel BS,
official cover "Moderne Architektur in Basel - Tag der Briefmarke - Journée du Timbre - Giornata del Francobollo - Di dalla Marca Postala- BASILEA 2001 - Offizielle Ausgabe VSPhV / FSPS / FSFS", 
with add-on cancellation UN "BASEL 7.-9.12.2001 - Tag der Briefmarke - Postverwaltung der Vereinten Nationen",
cancelled "5.3.2002 United Nations New York (UNO NY)", backside arrival cancellation "11.3.02 8706 Männedorf",
delayed mail delivery due to the World Trade Center (Twin Towers) attack on New York on 09/11/2021,
The mail was also irradiated (anthrax attacks), the envelope was slightly discolored - a real contemporary document!