The window envelope is an envelope with transparent plastic window in it so you can see what it is and who it's from. It was invented and patented by Americus Callahan in 1901. It was first called an "outlook envelope." Callahan planned to use very thin rice paper as the window, but now clear plastic is used.
References[change | change source]
- "US Patent 701,839". United States Patent and Trademark Office. Google. Retrieved 5 June 2007.