After I cleaned this took me a few days to find out what this was. No other detectorist I know had any idea and never saw one. Turned out to be a Spanish Patriotic coin button that was manufactured in Spain or Mexico maybe in the mints themselves between about 1720 and 1800. These buttons were patterned after the 8 Reals and a lot of the varieties were dated just like the coins. Apparently these were popular in the colonies and worn as an "in your face" to the British before the Revolution. Most were linked (cuff links) as this one was but they were usually separated early on as a result of the thin link made for them. Thus supposedly very rare to find a linked set. Site I found them in dated from the 1740's so fit right it. This one is dated 1764. Having a lighting issue with the pics but think they're ok.