This is an ambrotype photograph of some lost to history fellow. I can find no easy (or rather succinct) way to describe the "ambrotype" process, so if you want detailed information on how these photos were created, you can find it online, easily.
Essentially, an ambrotype is a photograph developed directly on glass. If I understand correctly it is sort of a reverse negative, so it looks like a positive, if that makes sense. Lots of chemicals & precise timing were involved, and I have no idea what kind of camera was used to create this kind of photo.
Ambrotypes were popular in the 1850s & 1860s, and there is a decent chance that this particular one pre-dates the civil war, making it one of the oldest photographs we have.
It is not in particularly good shape - there are a lot of surface scratches. And its just a formal portrait of a person's head, so its a pretty typical subject. But it is the only ambrotype I have, and it IS a photograph on glass made over 150 years ago, so that's pretty cool.
