Windowed envelope

US Patent 701,839 for a windowed envelope
Modern envelope with a single window for the recipient address

A windowed envelope is a conventional envelope with a transparent (typically PET or BOPS Bi-oriented polystyrene[1] plastic film) window to allow the recipient's address to be printed on the paper contained within.

  1. ^ "PROCITE Films". Archived from the original on 3 June 2013. Retrieved 7 June 2013.