I love portrait coins! I'm not sure who is on the coin...if you provide weight and diameter, it might be easier to identify.
I have to agree. I don't recognize the personages. But 20 euros would make me buy it just for the mystery of it.
From the few of the types I have run across, the combo of Agrippina and Caligula seems possible and it's just as possible, IMHO, that it could be Tiberius and Livia.... but the coin looks more like a bronze than a silver coin. Can you identify any of the legends?? And what made you believe it is Agrippina senior?? In any case, a very cool coin for the price!!! Hope someone can pin it down for you.