23mm, Post Civil War/Indian Wars/Spanish-American War era New York Troy Citizen Corps (6th Reginment National Guard) Coat button with a "Ridabock & Co / New York" backmark. Plated. This button was made circa 1880's-90's and is a great looking, well designed uniform button. 
The motto ILLIUM FUIT TROJA EST surrounds the knapsack on a garter.  It is a quotation from Virgil's Aeneid and was adopted by the City of Troy, N.Y. as their motto.  Quoting directly from Wikapedia, "Troy's Latin motto is Ilium fuit, Troja est, which means "Ilium was, Troy is".[a]Northern and Western New York was a theater of the War of 1812, and militia and regular army forces were led by Stephen Van Rensselaer of Troy. Quartermaster supplies were shipped through Troy. A local butcher and meatpacker named Samuel Wilson supplied the military, and according to local lore, stamped the meat barrels "U.S." which alternately was interpreted as "United States" and "Uncle Sam," meaning Wilson. Troy has since claimed to be the historical home of Uncle Sam, who is buried in the historic Oakwood Cemetery located on the northern outskirts of the city and the burial site of numerous local luminaries."