This is a silver billon coin. But it looks like bronze.

My only Nero yet. I would have lone with Poppaea if I could find it, the female figure in this one is a representation of Alexandria with an elephant skin on her head. The LIB is missing the B but it must be year 12 of the reign of Nero. This bust was a single year issue. RPC I 5289, 65-66 AD
They really used very little silver in these coins in Nero's time. Later under Hadrian the tetradrachms of Alexandria are noticeably more silvery in look.