I've seen these posted in CW sales before.
My hunch is that they date from the correct time frame to be CW. The last Eagle button we found was marked "Extra Quality." Found with two other Buttons (one with the same backmark) at an old civilian site predating 1880. The only other thing we found there was an 1861 Indian Head Cent.
I don't see mention of these buttons in Albert's button book, but perhaps others on this forum might have more information to share...
Regards,
Buckleboy