The first currency of the Estonian Republic was the mark. It was introduced in 1918 and tied to the German ostmark. It remained in circulation through the late 1920s, at which time the kroon became the new currency. I have heard interesting anecdotes about Estonian children finding stacks of old 1000 marka or 100 krooni bills stashed away in attics during the Soviet era, and presenting them to their parents and grandparents who just shrugged as if they really had no recollection of seeing them before. Interesting that the Estonian mark was once pegged to the German ostmark, just as the reintroduced kroon was once pegged to the Deutsche Mark and later the euro, before full euro adoption in 2011.
It is a good example of the centrality of Germany’s influence on the Estonian state.