Privates, 12th Infantry Regiment, Pennsylvania National Guard, c. 1910.
The keystone on the cap badge and collar instantly identifies these two men as members of the Pennsylvania National Guard. Written on the back of the photograph are "Bloomsburg," "Thomas," and "Boys." Before the First World War, Bloomsburg was the home of companies from the 12th and then the 13th Infantry Regiments, but even under enlargement I cannot make out the unit numbers above the crossed rifles on the cap. On the collars, though, I perceive the number to be 12.
Page by Mark Conrad, 2010.