- The first known "envelope" is dated back to between 3,500 to 3,200 B.C in the Middle East. Unlike what we use now, these envelopes were clay spheres molded around financial tokens.
- Paper envelopes first used in China in the 2nd Century.
- The first envelope making machine was invented in 1845.The paper was diamond shaped and did not come pre-gummed for sealing.
- In the Victorian Era, the placement of a stamp were used as coded messages between young lovers whose parents censored their mail. For instance, an upside down stamp meant "I love you" a diagonal stamp means "I miss you".
- The classic #10 business envelope. Measuring 4 1/8" x 9 1/2", the #10 is the most commonly used envelope, and it perfectly fits a tri-folded 8.5x11 piece of paper. At Precision Envelope, #10 envelope printing is a huge part of what we do, and is the envelope most frequently used by businesses.
- When creating printed wedding invitation envelopes, it is proper to spell out house numbers under 20.
- A chemical company recently created an envelope made of “spunbonded olefin”. This envelope looks like and can be written on just like paper, but it is insensitive to water and chemicals and is virtually impossible to tear.
- In 19th Century England, the recipient would pay the postage of the envelope. Correspondents figured out a scheme to transmit brief messages through prearranged envelope marking. The recipient would decode the message, then hand it back to the postman, refusing payment. Postage stamps were created in order to put an end to this.
(Sources: http://allamazingfacts.com/Invention-of-Envelopes/245.php, http://en.wikipedia.org/wiki/Envelopes)