THunter is correct. This is a jeton, a type of token. There is a wikipedia piece on it. I found one there which I consider one of my favorite finds. A guy in the First State club hammered the ever living pee out of it in the very beginning, before it was closed off, and found many good finds. I went with the club pres soon after the site was opened back up. First trip I found a jeton of George II. It was in perfect shape, it was as thin as a piece of paper and read about 4-5 on the XLT, foil area in other words. A guy had warned me of just this type of find right before I found it.
We hit it maybe 6-7 other times, including once during a gale which was cool. I have never found fewer metal items per time invested, but what I did find was very cool. I eyeballed a wooden domino which was way cool.
The site starts right at the parking area just beyond the Yacht Club. Minimal chances of metal targets except after storms, but pottery should still be available off and on. The local museum in Lewes requests that you show them what you find for recording; they told me for example mine was the 2nd domino reported.