What is this?

I know nothing about these.  It appears to be a cob?  Any idea what it is?  Apologize about the pictures, they are from a cell phone.  I will try to get some better snaps if needed to id.

Appears to be a Mexico minted 1/2 reale.  Very blurry pics, either back up a little, or use a regular camera on macro.  Cant really tell much from these pics.  But yes, it is a cob.

Yes, definitely a Mexico half-real... The first two pics are of the cross side; shrunk down (see below), you can clearly see the lower L lion, much of the cross, and bits of the upper R lion and lower R castle. That lion style (walking zombie stick-figure) places it right around the early part of Philip V, from about 1701-14. It's remotely possible that this could be late Charles II (no earlier), but every lion style I've seen on a C. II half real is some variant of horizontal-situated rat-cat; have never seen the style of your piece NOT on Philip V. The planchet is the common "teardrop" shape of that late 1600's-early 1700's period.

Can't make anything out of the monogram side from that photo (the last pic is of that side)... there isn't much left there. Perhaps a clearer shot might allow you to see the vague outline of the monogram, which again, should be be Philip's PVS, with a small chance of it being Charles'.

Given the sea-corrosion and the date range, I'd assume this is from the 1715 Fleet.

Wow, thank you so much for the info.  I will see if I can get some better pics up here in the next day or so.  Much appreciated you two!   

Realeswatcher, you are amazing with what you can tell from those pictures!