I was putting my metal detectors in the car today when I spotted a button in the dirt next to an 1800's house. Do you have any ideas of the age of this button? It is a two piece button with a stamped design.
You asked how old your button is. It has a the "pierced dome" variety of what is called a self-shank back... which (if I recall correctly) was invented and patented sometime in the 1890s.
On your button, the dome's center is broken out.
That form of back was invented to be a very inexpensive alternative to manufacturing buttons with an "applied" loop. In this manufacturing process, a machine simply presses a thin disc of sheetmetal to have a small dome at its center, with two holes pierced into opposite sides of the dome for sewing the button onto clothing. There's no need for the materials-& labor-cost of buying wire, shaping the wire into a loop, and attaching it to the button's back. See the photos below.