Moses Billings
With the development of the daguerreotype in the 1840s, the role of the portrait painter declined in general, because it was now much easier and much cheaper to have one's likeness presented in a visual format. While many portrait painters lost business in competition with the daguerreotype, Billings instead began to produce daguerreotype prints himself. It is not known exactly which prints were made by Moses Billings, as daguerreotypes were usually signed, when signed at all, along the side of the plate. Due to the traditional storing methods of daguerreotype plates, even this signature usually quickly became illegible. However, it has been generally noted, or at least hypothesized, that his daguerreotype prints showed a level of talent and artistry above that of amateur daguerreotypists. Though it is not known exactly which prints were his, it is known that he had largely abandoned the process by the 1850s. Even after he stopped making daguerreotypes, he did continue to paint people's portraits on canvas.
Daguerreotype
Conservators were able to determine that a daguerreotype of Walt Whitman was made in New Orleans with the main clue being the type of frame, which was made for wall hanging in the French and continental style. Supporting evidence of the New Orleans origin was a scrap of paper from "Le Mesager", a New Orleans bilingual newspaper of the time, which had been used to glue the plate into the frame. Other clues used by historians to identify daguerreotypes are hallmarks in the silver plate and the distinctive patterns left by different photographers when polishing the plate with a leather buff, which leaves extremely fine parallel lines discernible on the surface.