Not sure, but use a toothpick only to clean it, unless you have some Andre's pencils. It may be a Confederate staff officers' cuff. The eagle faces the wrong way for a Union eagle button, but I can't swear to it!
Is it one two or three piece? Do the eagles wingtips point up or down. Please post some after cleaning pictures. My old eyes can't make out much detail.
Ok, that is better. Two piece button, this is, after 1835, eagle facing right with wing tips down, wing elbows up, split wreath at bottom with a ring around the entire eagle. Correct?
What else did you find? I do have an idea, I'm checking it out.
I think it's a Confederate officers' button. Albert's CS-43 is similar in design. I can't find an exact match, but I think it's a local manufacture, and the "puffed" feature is sometimes seen on Confederate local buttons. I believe some of the Louisiana buttons that were locally made were made in this fashion. Any evidence of stars above the eagle? I can make out three arrows in it's left talon (our right side looking at it). That rim is quite unique. It's quite a nice find!
OK, that would be GI 63Bv on page 32/33 in Alberts book. Except the wing tips on that button point up and you stated the tips on your button point down.