Welcome to Numista. Weight, diameter, and best guess at composition is always helpful in attempting to identify a coin. Not much info left on this example so the more information you can provide the better. I altered the photos to better help in identification. I see the beginnings of Philip and an IM or possibly JM next to the Castle but so far I cant find a better match than you have already found as well.


Edit
Here is a 2 Maravedis Philip II with the IM initials, no date and no dots but Circa 1580-1587. Beginning to believe it is from the Philip II era,.
.https://en.numista.com/catalogue/pieces45121.html?mobile=0