In the map

Sri Lanka is a big island next to India

The name of the country is Taprobana

There are hills and mountains in the middle

There are many rivers which start from the mountains

The names of the cities are, Anurogammi, Nagadibi

Sri Lanka is a small island next to India

Sri Lanka was called Taprobane a long time ago

Sri Lanka has a central hill area

The rivers start from the central hill area

The current names of the cities are, Anuradhapura and Nagadeepa

So, this is the big story behind the small stamp.