I created a special magic item that I wish to share with everyone.  The item is called the Twin Quills of the Phoenix (or whatever bird you wish to use, Roc, Cockatrice, Couatl, feather winged demon or devil, feather winged air elemental, griffon, harpy, hippogriff, lammasu, Pegasus, shedu, Sphinx, feather winged celestial or angel ...).

The quills are always made in pairs.  The first quill is placed on a writing desk.  The second quill goes through the exact same motions as its partner.  So the "intended use" is to allow a Bard or Scribe to make two copies at once by setting up one quill on a desk with ink and paper at the same time the second quill is arranged the same way.  When the quill is activated both quills are "picked up" at the same time, dipped into the ink well and put to paper with the exact same fashion.  The user get two exact copies of the document.  It was intended for the Realm to make identical copies of a decree or charter so one could be handed over for processing and the second one sent to the archives.

Initially only a few of these twin quills were enchanted (they must be the same feather from opposite wings of the creature, ritually cleaned and then put through a number of enchantments).  The archivist used these to make the documents most important to the king.  But later they realized this permitted the other officials to transmit copies of documents over long distances.  So a Duke, 100 miles away, could make a decree and it was written down.  Then the original copy was sent to the archivist who copied the document for the Duke's archives.  But by using the Twin Quill an additional copy was made at the archives of the king at the same time, and the king would be told of the decree.  This enhanced the control of the king enormously and they learned to use it in other ways.  They came up with a signaling system using a red and a blue ink bottle sized bottle of water.  The quill normally rested in a bottle of water and the bottle was clear glass.  If the duke wished to send a message to the king he would have the quill moved to the blue bottle of water.  One hour later, he would have his archivist write a message and then place the quill in the clear bottle of water.  If the king wished to send a message to the Duke he would have the quill placed in the red bottle and then one hour later they would write the message to the duke and move the quill to the clear bottle.  The utility of the Twin Quills was so great that many more were produced and distributed to the top government officials.  It was also a state secret that they existed at all or where they might be found.

Eventually the bards of the diplomatic corps were granted some Twin Quills.  They likewise used them to transmit diplomatic correspondence when it was a high priority but they were not in an established governmental seat of power, such as working in an embassy somewhere outside the country.

However, word leaked out when the quills were first created because it didn't seem to be an important secret that the archives would have a copy of a document.  It was when they realized the quills could be used to send and receive messages that their power became evident.  But initially they didn't think of the nefarious purpose that these Twin Quills could be used.

Rogues found out about them and they figured out what they could also be used for.  They were the ultimate tool for the forger.  One quill could be placed at the desk of a high government official and everything he wrote could be read.  Worse, copies of his signature and handwriting could be collected and used.  If a particular forgery was necessary, and it had to be the very best quality, it could be prepared ahead of time and when the leader went to sign some mundane letter the forgery could be slipped in at just the right moment and effectively signed by the official himself.  Rogues among some small groups guarded this secret more carefully than the government.  They needed to keep this power away from the knowledge of the government and they wished to keep an advantage over rival guilds.

Now in addition to their duties as Diplomats, members of the Bards Diplomatic Corps are charged with keeping account of all the Twin Quills, finding and destroying any that fall beyond their accountability (like the Secret Service does today for the Treasury).  To do this, they only need to destroy one.  But it is often worth considering allowing the other party to keep theirs and feed them disinformation.  Such is the game of espionage.

That sounds very cool, and it has some background. Would this be a wondrous item? 

Well, I wouldn't classify it as wondrous because there are many of these in circulation.  Maybe Very Rare, or super extra rare would be appropriate.