German ostruble

Ostruble (German and Polish: ; Latvian and Lithuanian: ; ) is the name given to a currency denominated in and , which was issued by Germany in 1916 for use in the eastern areas under German occupation ( and the Government General of Warsaw). It was initially equal to the Russian ruble. The reason for the issue was a shortage of rubles. The banknotes were produced by the in (now ) on 17 April 1916.
From 4 April 1918, the circulated alongside the in the area, with = 1 . In the Government General of Warsaw the was replaced by the Polish on 14 April 1917.
Denominations.
The denominations available were:
The front sides of the banknotes carry a warning in German against forging banknotes. On the reverse sides is the same warning in Latvian (with old style orthography), Lithuanian and Polish.
There were also 1 kopeck, 2 kopeck and 3 kopeck coins, made out of iron.
Aftermath.
The circulated in Lithuania together with the Ostmark until 1 October 1922, when it was replaced by the .
It was also still in use in a part of the Second Polish Republic during the first months of independence, until 29 April 1920.