The Struve Geodetic Arc FDC

The miniature sheet indicates the six points located in Finland.
The two stamps in the release are within each other in the miniature sheet.
The outer stamp is round, and the inner has the shape of the map of Finland.

The Struve Geodetic Arc was used for determining the size and shape of the globe.
The arc, which is approximately 2,820 kilometers long, extends from the Black Sea in
Ukraine all the way to the Arctic Ocean in Norway. The arc was named
after F.G.W. Struve who managed the measurement in 1816-1855.