Good morning collectors! First, I have some good news for those wondering where the heck the German States are: I annotated a map of the Pre-Unification German States and attached it to this post. I also added flags on the map for people that are interested in that. Today's topic is the coins of the Grand Duchy of Oldenburg.The Grand Duchy of Oldenburg was founded in 1815. Previously it had been a county (from 1535-1773) and a duchy (from 1774-1810), using different money along the way. Before that, it had been a semi-autonomous state inside Saxony. Oldenburg had been owned by Russia, occupied by Napoleonic France, and finally gained complete autonomy after the dissolution of the HRE. Following the Congress of Vienna in 1815, Oldenburg was granted the status of Grand Duchy. It joined the German Empire during the German Unification of the 1870s. The ruling family was the House von Oldenburg, also the kings of Norway and Denmark at the time. I stopped counting the results of "Oldenburg coins" when I looked them up: Norwegian, Danish, Swedish, Oldenburg-ish, and even Greek coins showed up because the von Oldenburgs ruled over those places at different times. The monetary system of the Oldenburgish (?) Thaler is surprisingly straightforward, but it would be awkward to use. 1 Thaler = 30 Groschen = 72 Grote = 360 Schwaren. Oldenburg used this system from 1811 to about 1870. Then, they adopted the German Mark right before joining the German Empire. Oldenburg minted their coins in a mint in Oldenburg, which makes sense (especially since I don't know much about Oldenburg except for a few coins and some royal stuff). They based their Thaler off the Prussian Thaler when they reformed their money in 1815. The coins of Oldenburg were standard German States coins, usually featuring the Duke on the obverse and a coat of arms on the reverse.One coin I found interesting while researching this was actually minted post-unification. It is the 10 Mark coin of Nicolaus Friedrich Peter from the 1870s. Nothing really distinguishes it from the other coins (similar obverses and reverses), but it was one of the first Oldenburgish coins to use the German Mark denomination and standard of gold fineness (.900). The Prussian-based German Empire sought to unify Germany's economy under one monetary system with universal denominations. In that, they certainly succeeded, creating a decimal, empire-wide monetary system that lasted until its defeat in WWI.Thanks for reading, and happy collecting!Learn more:Numista -> Grand Duchy of Oldenburg, World Coins chatBritannica -> House of Oldenburg, Duchy of Oldenburg