Very nice James, but I don't believe that your 1766 cut coin is spanish. The spanish silver coins minted between 1732 and 1772 were called milled pillar, and your buddy's 1755 half reale is one of that type. But all of these had the bottom of the date facing the outside edge of the coin, and yours is opposite from that. I don't immediately recognize it but will look into it if I get time. It's also unusual to have the entire date appear on a cut coin as the practice was to split the date down the middle. And it's even more impressive that the entire 4 digit date was left on a small 45 degree wedge (smaller than the 1/4 as you stated). Also, based on a size comparison with your 1815 half reale, I'd have to say your cut coin is from a larger denomination. Very unique and interesting find. If you can post some close-ups of both sides with good detail it would be of great help with ID'ing it.