Complex sentence: The coat of arms of Oldenburg is the coat associated with the state of Oldenburg, a county, duchy and grand duchy, that existed between 1180 and 1918, and the associated with the parts of the House of Oldenburg that ruled the state.
Split into simpler sentences: The coat of arms of Oldenburg is the coat of arms associated with the state of Oldenburg, a county, duchy and then grand duchy that existed between 1101 and 1918. The arms are also associated with the parts of the House of Oldenburg that ruled the state.