Nails are helpful clues for dating historic buildings.
Lee H. Nelson of the National Park Service provides a chronology of nails and methods for discerning the general time period of a building’s construction.
Gathering samples of nails can also show if a building was built at one time or over a span of time.
Nelson provides an explanation of hand wrought and machine made nails with diagrams of how different nails look and how they would have been constructed.
Technical Leaflet #48 (1968)
For more information on similar topics, please refer to Technical Leaflet Bundle 2, Historic House Restoration: Getting Started, and Technical Leaflet Bundle 24, 21st Century Top Five.