It could be a little older than 50 years. The patriotic motifs have been around on commercial items for a long time. If the site is mostly pure than possibly a returning veteran could have worn it on his coat since it is s imiliar the the droop wing eagle favored by CS forces. Though there are unpublished CS buttons I only know of two. I have not personally seen this button before it just does not have the right look to it. The little micro dots are problematic and suggestive of later manufacture. Patriotic 'Navy' type blazer buttons are found all the time and are commonly mistaken for earlier navy button. I study buttons closely and have an example of every issued branch of service, and every state north and south in my collection. I do not believe this to be a pre-1865 button. But I can see the resemblance to the preferred southern droop wing patriotic style. I just think it was easier to fit a bigger eagle with droop wings on this particular button by the manufacturer. And that is not to say the maker had not seen a southern droop wing button and was loosely basing it on this potentially for market in the post war south. But that is just pure speculation. A pic of the back would be more conclusive. Southern war time iron backs are pretty easy to tell. But I am guessing this example is a flat type back more associated with later buttons. Good luck at the site and there has to be some nice relics lurking about.