If it is the size of a dime, it cannot be the Ethiopian version of a dollar. To be correct, the dollar size silver coin of Ethiopia is denominated as a 'birr'. According to Krause, the nearest coin to a dime for Ethiopia is the 1/20 birr, and was struck between 1903 and 1928, so it must be fairly common.
I would't get crazy about a big value for it, in the condition you have pictured.