I hear you, Mike. Still waiting on one field to be plowed down this way this late in the year!
As to the early stuff, I've found Marine buttons a couple hundred miles inland at late war sites. A buddy even found a New York at a very late war site. By that time it should have been all eagle buttons as the U.S. Army was identifying itself with the new central government rather than the state governments (New York, Connecticut, Massachusetts, Pennsylvania, New Jersey buttons, etc).
But with Beaufort, SC having been held since late '61, I believe when Sherman came through he took some of those coastal troops with him or his own troops picked up souvenirs as they made contact with the coastal troops. This explains the early stuff in late war sites farther inland than they ever should have been.
You may have the same situation. A late war unit did a bit of trading with an early war, or coastal unit.
Just my two pence.
Good Hunting!
Richard