The Magento_CurrencySymbol module contains not only the «Currency Symbols» functionality but the «Currency Rates» functionality too which is inconsistent with the module name

Issues
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1

https://github.com/magento/magento2/blob/2.0.0/app/code/Magento/CurrencySymbol/Controller/Adminhtml/System/Currency/FetchRates.php

https://github.com/magento/magento2/issues/3098