Trez, Your assessment appears to match this coin very closely. Unfortunately, it appears as though about 1/4" has worn off around the edge making it very difficult to read the script. However, it is made of copper and it does have the lion and castle on the obverse and reverse. I'll continue to research in hopes of figuring out it's exact identity. By the way, it was given to me when I purchased a used Excal recently. The owner thought it had some value. A local coin dealer recently offered me $2 for it.
Penz,
1602? How did you come up with that as the date range.
I think its actually earlier than 1500s...try looking into Blanca de Enrique III (1390-1406)
Good luck,
Scott