A registered cover sent from Alexandrovsk Post on Sakhalin Island to Vienna. Postmarked at the field post office of the 5th Siberian Army Corps on 25.2.06, and in Vienna in April. The Alexandrovsk post office closed on 12 July 1905 when the Japanese occupied the town. In late October a field post office was established by the newly arrived Russian troops (units of the 5th Siberian Army Corps). Sent to the editor of the Journal of the Society of Drilling Engineers by German mining engineer Friedrich Kleye, who arrived on Sakhalin in 1898 to explore for oil on the northeastern coast. With British money, Kleye, known as the "pioneer of the Sakhalin petroleum industry," established the Sakhalin and Amur Oil and Mining Industrial Syndicate. A strait near Chaivo on the northeast coast of Sakhalin is named for him.