Bulgarian vehicle plates have letters indicating in which province the car has been registered. Does your country have a similar system? : r/AskBalkans
Old Bulgarian License Plates / Старые номерные знаки Болгарии - Page 3 - (BG) | Bulgaria - PlatesMania.com
File:Bulgaria-automobile-license-plate before 1986.jpg - Wikimedia Commons
Bulgaria
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Bulgarian 6 zeros license plate : r/mildlyinteresting
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Bulgaria Car Plate. Vehicle Registration Number Stock Vector - Illustration of metal, european: 127252703