This is an illustration of the unique “Bordeaux Cover”, or “Bordeaux Letter”, which has both of the <a href="https://en.wikipedia.org/wiki/Mauritius_%22Post_Office%22_stamps" class="extiw" title='en:Mauritius "Post Office" stamps'>Post Office Mauritius stamps</a>.
Source:  <a rel="nofollow" class="external free" href="http://www.glenstephens.com/bordeaux.jpg">http://www.glenstephens.com/bordeaux.jpg</a>
Original uploader was <a href="https://en.wikipedia.org/wiki/User:Fconaway" class="extiw" title="en:User:Fconaway">Fconaway</a> at <a class="external text" href="https://en.wikipedia.org">en.wikipedia</a>
31 July 2007 (original upload date)
Transferred from <a class="external text" href="https://en.wikipedia.org">en.wikipedia</a>