Help ID 1/2 real

Hey,

I'd appreciate some help with the ID of this coin, sold as a shipwreck ½ real from 1600's. 

It has a diameter of approximately 15mm, but I do not have a scale to tell the exact weight.

The cross on the reverse, plus what seems to be a castle /lion made me exclude Mexico city and think of Potosi or Lima.

The obverse is a bit more complicated, but I think I can see a V which made me think of Philip III*.

Any idea?

Thanks,

Bruno

*If I put the coin backlit there seems to be a V also in the part with the patina, but because it's not elevated, I'd believe more the highlighted V.

Regarding the V you highlighted, could it not be the upper right negative of a S instead?

Mmm I'm 99% sure that's a V, because it's too clean to be anything else :D