// Most keyboards have the EuroSign engraved on the E key
partial
xkb_symbols "e" {
    key <AD03>	{ [  NoSymbol,   NoSymbol,   EuroSign,	NoSymbol ]	};
};

// Many Apple keyboards have the EuroSign engraved on the 2 key
partial
xkb_symbols "2" {
    key <AE02>	{ [  NoSymbol,   NoSymbol,   EuroSign,	NoSymbol ]	};
};

// Some keyboards have the EuroSign engraved on the 4 key
partial
xkb_symbols "4" {
    key <AE04>	{ [  NoSymbol,   NoSymbol,   EuroSign,	NoSymbol ]	};
};

// Many keyboards have the EuroSign engraved on the 5 key
partial
xkb_symbols "5" {
    key <AE05>	{ [  NoSymbol,   NoSymbol,   EuroSign,	NoSymbol ]	};
};
