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The Padlock Patent Archive

Three centuries of keeping things shut

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Twelve-bolt lock

Patent drawing showing a padlock's oval case with U-shaped notched shackle, internal stacked latch plates with springs, and an ornate warded key.

IMPROVEMENT IN PADLOCKSWilliam P. Wirth and Theodor H. Wichert · April 1, 1879

United States patent drawings and specifications are works of the U.S. government and are in the public domain — they were never copyrighted. Download them, print them, frame them. Our commentary and descriptions are © 2026 The Padlock Patent Archive.

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