History of Sealing Wax ( from www.nostalgicimpressions.com They include a printed romance card bearing the following info, with every wax seal that is purchased from them. There are more detailed histories available.)
Since time immemorial, the seal has served as a stamp of indisputable authenticity, just as a signature is accepted in the world today. The use of seals can be traced back to the Old Testament, where it mentions that Jezebel used Ahab's seal to counterfeit important documents.
Royalty and governments used their own seal to affix to proclamations to give them their authoritative stamp of approval. The first Great Seal of England was that of Edward the Confessor, impressions of which can still be found. During this time, almost everyone had their own seal, and while most people had just one, Royalty would own several, including their "Great" Seal, as well as seals for all their courts and officials. It was common practice to destroy the seal when the owner died, which is the reason so few original seals are still in existence today.
Official Seals of the Crown were often handed over with great ceremony, and in Medieval Times the size and motif of the Seal conveyed an image of the status of it's owner. Early motifs were equestrian or heraldic in nature, or showed the owner in various pursuits like hunting or doing battle. William the Conqueror used an equestrian seal showing him armed and ready for battle.
In Medieval Times, betrothals were prearranged-therefore true words of love were secretly written and the envelope's contents secured by a wax seal, so that the recipient could be assured that their passion would be unknown to others.
The first Seal of the United States was created by Benjamin Franklin, John Adams & Thomas Jefferson on July 4th 1776 immediately after the Declaration of Independence was signed. Congress realized the necessity of such a seal for the newly established nation.
As literacy increased, seals were used less frequently and with the introduction of the gummed envelope in the 19th Century the need for privacy was reduced. Seals became a more personal expression as well as a decorative embellishment.