Doubled Serial Number Digit Errors: When a Single Numbering Wheel Strikes Twice on the Same Position and What These Sell For
Doubled serial number digit errors rank among the most visually dramatic and mechanically fascinating misprints in U.S. paper money collecting, yet they remain widely misunderstood even by experienced hobbyists. This guide breaks down exactly how these errors occur, how to authenticate them, and what the current market looks like from common examples to genuine showstoppers.
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