There’s no doubt that this image is a cabinet card. Through the latter half of the 19th century, card photos of various sizes, shapes and colors were commonplace. The brown card of this image dates it to the 1880s.
This fancy studio backdrop imitates a living room. The style of furniture painted in the background can help date the image, too. The tall piece to the left is common throughout the 1880s.
Every part of a military uniform has clues worth studying. According to a quick Google search, the hash marks on the sleeve indicate the man was a non-commissioned officer (a sergeant or equivalent).
The owner of this image wondered if this was her German ancestor posing in Germany, but the belt buckle emblazoned with US changed her mind. The American army admired German military methods, and so began wearing spiked headgear as a tribute around 1880.
The owner thinks this man is her great-great-grandfather (b. 1816). But if this photo was taken in the 1880s, her great-great-grandfather would have been in his 60s or 70s (much older than the man in this photo looks). More research will be necessary to identify likely subjects.
A version of this article originally appeared in the July/August 2019 issue of Family Tree Magazine.