Private Albert H. Davis of Company K, 6th New Hampshire Infantry Regiment 1861 [via Library of Congress] * click on image for a larger view8
Tintype photos, as the name implies, were photos with the image on a metal surface, rather than on glass or paper. Tintypes were produced in the USA from 1856 and became popular from the 1860s. They remained popular into the 1900s and as late as the 1920s.
1/6 Plate Tintype of a Young Federal Drummer.