Several items on the Army’s Service Cap—hatband, chin strap, cap device, embroidery—are used to denote the rank classification and branch of the wearer. But there’s one item that remains the same on the cap regardless of the wearer’s rank: the screw-buttons used to secure the ornamental chin strap at the rear of the cap. This standard cap-screw button features a rendering of the coat of arms of the United States, i.e., the obverse side of the Great Seal of the United States.
It is the same imagery found on the buttons of Service and Dress uniforms worn by all Army personnel save those in the Corps of Engineers; both Officers and Enlisted personnel in that branch wear
buttons with the famous “ESSAYONS” design that dates back to some time in the first two decades of the 19th century.