I don't know if this is a good button or not I found in an old farm field about 12 inches down. I think it might be just a button off an old coat but I don't know for sure.
I hate to be a killjoy but that appears to be a modern blazer button. The iron back is usually a dead give away and that is a popular motif for civilian blazers. Of course, I could be wrong.
I hate to be the bearer of bad news but alas that's just a modern era blazer button and not military at all. I'd say from the 40's maybe 50's.They're dug all the time throughout the country and guys always think they have a good early button .Here's some real civil war period Navy buttons I've found in civil war camps both union & confederate in South Carolina.