On September 21, 1847, the famous Mauritius “Post Office” stamps were issued by the British Colony Mauritius. They are among the rarest postage stamps in the world and a letter with both stamps on its cover is estimated to be worth more than 4 Million US$.
Mauritius Postal Service
In 1772, the very first postal service opened up at Mauritius. In Great Britain and Ireland, the first stamps were available in 1840 and Mauritius intended to follow this example. Finally, in 1846 the order for two stamps in red and blue as given. Since the process of making stamps at this place and time was pretty complex and only one stamp at a time could be produced, only 500 red and blue stamps were made and found in Mauritian stores on September 22. On the left side of the stamp, the words Post Office were printed instead of the usual Post Paid and rumors circulate until this day if this was a simple mistake or if the printer had too bad hearing and failed the right words.
Due to its rareness, the stamps had a pretty high value from early on and were traded very often. There is even a record list of people who have owned the most amount of the stamps at one time. From the still existing blue and red stamps it is also noted in detail, if they were used, unused or even were they were sent to. The famous Bombay letter is presumably one of the most rare and expensive letters of all times. Two blue Mauritius were stuck on it and addressed to a clergyman in Bombay. In 1906, the famous collector Alfred Lichtenstein bought the letter and since then, it was traded various times and is now owned by a Russian collector. The price of stamps varies highly and depends on how well they are preserved. A used, but well preserved blue Mauritius is estimated to have a value of about 1 million Euros.
Until this day, there is no other stamp that reached the same popularity as the Blue Mauritius even though there are some that are even more seldom and more expensive. In 2011 there was a unique exhibition in Berlin that showed 18 stamps at the same time.
At yovisto, you may enjoy a video lecture on ‘The Art of the Stamp’ by Maynard Sundman.
References and Further reading:
-  Blue Mauritius Research Companion
-  Mauritius Reprint from Original Plate
-  The RMS Britannia and the Transatlantic Postal Service, SciHi Blog
-  How Anthony Trollope invented the Red Postal Box, SciHi Blog
-  The Mauritius “Post Office” stamps at Wikidata