Just a note on the Przewalski Horse and the Berlin Zoo that Ben Trumble mentioned earlier.

The above postmark was produced to commemorate the 100th anniversary of the discovery of the Przewalski horse, and the Berlin Zoo's ground breaking effort's at it conservation, and the sheet below was issued at the same time, by the Mongolian government to commemorate it's place of origin and to honor Dr Hecks/Berlin Zoos efforts on the "P" horses behalf.