What Do You Call A Piece Of Paper,

that measures less than 1.5" inches square that is worth $9.5m (£5.6m)?

 the 1856 British Guiana One-Cent Magenta stamp, it has a long history being owned in it's time by a school boy, a Count and a murderer amongst others in it's history,

the details of the stamp can be better seen in this image of the 4-cent stamp of the same issue, and the good news is that it is now on display to the public at the Smithsonian, which is great news for philatelists, it is estimated that of the almost 140 years since being discovered,

 the One-Cent Magenta has been on view for a period of less than a month, these are the viewing times,

The 1856 British Guiana One-Cent Magenta, the world’s rarest postage stamp, is now prominently displayed in the museum’s William H. Gross Stamp Gallery for a 2.5 year period. The exhibition of the stamp will be the longest and most publicly accessible showing ever.

Please note: the 1856 British Guiana One-Cent Magenta may be temporarily unavailable for viewing should preservation, conservation or presentation issues unexpectedly arise. Please check with the museum in advance of your visit for specific exhibit dates and availability.

In addition, the stamp will not be on exhibit at the National Postal Museum on the following dates (subject to change):
November 27 — December 10, 2015
May 23 — June 10, 2016.

do I have one in my collection? I wish!