Daguerreotype c1840 - 1860
Louis Daguerre created the first commercial photographic process in 1839. It was produced on a sheet of highly polished copper. The exposure times were long and in the UK the operator had to pay a huge licence fee which made it a very expensive product.
It is quite easy to tell if you have a Daguerreotype in your collection. They are almost always in a case as it needs to be sealed away from the air.
They tend to have some amount of degradation starting from the outer edges,
The image is highly reflective and if you catch a light the image will look like a negative
Whatever you do, do not try and take a Daguerreotype apart or clean it. It can be damaged beyond repair very easily.