I have Stanton's Order of Battle. The 1994 Revision as well as the 1985 Edition. Along with his other books. All autographed. He was a neighbor when working on his Master's or PhD - I forget which (and it's not important anyway) - years ago in Baton Rouge.
Distinctive insignia, commonly called "DI's," are small badges of enamel and metal, usually about an inch or so in diameter and, in most cases, a variation of the unit's official coat of arms.
During the war, enlisted personnel wore them on the lapel of the service coat. Warrant- and commissioned officers wore them on the shoulder straps of the service coat and the khaki shirt. Since the war, they're worn on the shoulder strap by all ranks. In recent years, indivuals are allowed to wear the DI (one only) of the unit they served with in a combat theater above the right breast pocket of the service coat.
Unlike SSI's (shoulder sleeve insignia) or "shoulder patches", which are generally confined to units of brigade-size and larger, DI's were - and are - authorized for units from battalion/squadron to department/field army/command. Office of the Chief of Staff and Headquarters, United States Army have their own DI's.
For a relatively brief period, from the mid-1950's to the late 1960's, embroidered DI's, considerably larger than the standard badge-type, were allowed to be worn, sewn, centered on the right breast pocket of the service coat, field jacket and fatigue shirt.
If you're constructing a shadow box I may be able to locate one for you.