After the end
of the First World War the government of the new founded country
Serbian-Croatian- Slovenian kingdom took the decision to legalize
as means of payment for a certain period the banknotes of ex-invader
countries Austro-Hungary, Germany and Bulgaria. For the purpose
the banknotes from the above mentioned countries were count up
and sealed with special state seal. Here you can see some copies.
For more comprehensive information reed the book
of Kostadin Hristov "History
of Bulgarian paper money".