The key was invented by the master of Berliner locksmith Johann Schweiger and his company, Albert Kalkeri & co GmbH from Berlin-Gesundbrunnen, in 1912 to the patent pending. Today the through hole key used only still occasionally in old areas with corresponding doors and gateways, but it now is a popular souvenir of Berlin
The through hole key (also: Berlin, double key) is a key with two identical beards. After the closing of the lock, the key through the castle through can be slide and locking the door from the other side, without taking the key out of the lock. The through hole key facilitates the use of passage doors that locked should be kept closed so always only for a short time to go through, and then immediately back to lock. Such doors were often to be found in the Berlin housing with some several backyards (Berlin garden houses).
The through hole key works in conjunction with special locks, which prevent the pulling out of the key, if the lock is not locked. In this context is spoken also by a close constraint key, although the closure constraint is a property that depends solely on the Castle and not the key. The through hole key allows only the use of locks with a closing pressure in passage doors.
7.6 cm long without bracket
9.5 cm in length with bracket
Each key is unique because it is worn differently.
So are the images of sample photos
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