Appletons' cyclopaedia of applied mechanics: a dictionary of mechanical engineering and the mechanical arts (1880)
D. Appleton and Company, Benjamin, Park, 1849-1922 · New York, D. Appleton · leaf 315
302 LOCKS. … pose of the invention is to guard against a lock-out by the forgetting of a combination. Each of thetwo dials being set by different persons on a different combination, the lock can be opened by eitherperson in the event of the ethers forgetting his combination or being absent. Another feature…
Mechanical engineering -- Dictionaries
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