Any Help On An ID Not Sure What This Is ?

A Maria Theresa thaler. Probably about the most prevalent silver crown every made - and still being made. Nice clean uncirculated examples of the modern re strikes go for anything up to £20

I think you'll find that it is actually silver; it should be .833 fine, which is less fine than sterling. It certainly doesn't have the look of a modern Chinese replica. I'd assume the green spots on the high points came from being stored in a plastic coin album for too long; that should come off with acetone or methylated spirits.

As Bacchus2 implied, they have been manufactured in several different countries, and most of them were made long after the "1780" date which appears on them. They were mass-produced for trade in the Middle East, particularly the Red Sea region of Arabia and east Africa where the locals seemed to take a fancy to them. They do not bear clear and easily readable mintmarks, but slight variations in the artwork can reveal their origin and approximate date of issue. This website offers a summary.