It is easy to replicate a Daguerreotype effect using just the tools in Photoshop.
Not only were daguerreotypes black and white with a high contrast tonal range, they also had distinctive marks and scratches over the surface. This surface can easily be re-created using metal textures, set to a low opacity with the Lighter Color blending mode. Vignette effects are important too, to signify a low-quality camera. The Chalk and Dry Brush tips, set to Soft Light blending mode, allow for patches of dark and light areas to be randomly positioned.
When the texture and the vignette are set, you’re ready to add scratches and blemishes. These are made using the Brush and Eraser tools, with the Natural and Mix Media tips. Using a small size tip, randomly paint thin strips, each on its own layer. These can be bent and stretched with the Free Transform controls for a distorted pattern of scratches.