Made of brass with graduated slide for range finding of infantry and cavalry targets.
Frankfort Arsenal Sharpshooters Stadia. Made between 1854 and 1865; issued to sharpshooters and artillerymen for range finding of infantry and cavalry targets. Has a brass chain and bar for hanging from an upper button hold for ready use, and a twine cord with lead balls attached on either end. One connected to the stadia while the other was placed between the teeth, extended outward while holding at eye level to determine the correct range.
A scare sharpshooters tool, and a hard item to fine today.
I have added a reference on the use of stadium by soldiers in the field, with an illustration provided, from the manual, “Customs of Service for Non-Commissioned Officers and Soldiers ….Practiced In The Army Of The United States. by August V. Kautz, Lippincott & Co., 1864.“