Dave brought them over to my house and I had a look at them. They seemed to be a two piece, tin back button. They do not have a backmark. If the back is not tin.... it is something like zinc. They are not a threaded button, but some sort of a snap peice in the back. There was still some blue material still clasped in some of the snap peices. From looking at the back and the two piece design... my suspisions are that the buttons are from about the 1870's, probably a civilian coat. Can any of you button buffs out there verify this?