Enhanced Die Crack Mapping
The attribution of obverse and reverse dies occurs through a step by step process. Major die diagnostic such as date or mintmark positions are typically viewed first followed by secondary die diagnostics such as die cracks and die breaks. Dies developed defects during their usage. Die cracks are common die characteristics that appear on a struck coin as fine raised lines of metal. As a die ages, the die cracks can advance and become longer and heavier.
The inspection and recording of die cracks can be a long and tedious process. I have developed a technique entitled Enhanced Die Crack Mapping, which uses digital imaging software to record the exact location of die cracks via pictorial maps. An Enhanced Die Crack Map is created by tracing the location of die cracks on a digital scan with a black "electronic marker" while viewing the coin under a stereo microscope. This technique does have one limitation however. The thickness or strength of the die crack cannot be recorded, rather only the presence of a die cracks. The scope of this research effort did not allow for the mapping of die cracks on every coin where they exist. Instead I have used the Enhanced Die Cracking Map to illustrate later die states where the reader may have more interest.
The following Enhanced Die Crack Maps are from an 1856 San Francisco obverse die and an 1878 Carson City reverse die.
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