I recently received this daguerreotype from my mother's sister. I believe it's the oldest photographic image that I own. (I have a few ambrotypes - see My Third Great Grandfather and Pair of Ambrotypes as well as Alston Twins Circa 1860.)
From Maureen Taylor's wonderful Uncovering Your Ancestry Through Family
Photographs, as well as the PhotoTree website page on daguerreotypes, I learned a great deal about how to analyze this
The daguerreotype was introduced in 1839 and used for about twenty years until other photographic formats were introduced. Because the image is on a mirror-like surface, it appears positive or negative depending on the angle you're looking at. (It's hard to take a photo of it.)
The case, a quarter case (about 4" by 5"), appears to be what is known as a union case, patented in 1854, a more durable case than what had been available previously. According to Taylor's book, there are a variety of things to look at to help date the case: the design, the hinges, and the mat shape and design. (There are books devoted to this.)
There is no indication of who is in this photograph, so I will lay out what I do know about it:
In the 1850s, women wore their hair with these kinds of "puffs" on the
side of the head. Also in this time period, women often wore a lace collar like the one in this
photo. I think this looks like a relatively young woman in her late teens or early twenties, so born between 1830-1840?
There is a photographer's imprint in the lower left-hand side of the case:
A. H. Knapp
123 Wash. St.
A Google search of daguerreotype A H Knapp indicates that A. H. Knapp, a daguerreotype photographer, worked from 123 Washington Street in Boston for a very brief time in the 1850s. This suggests that she is not a maternal ancestor of my mother's (they all were in Allegheny County, Pennsylvania in the 1850s), but a paternal ancestor of my grandfather, Lowell Townsend Copeland.
I will share more analysis tomorrow with my theory of who this may be.