This copper plaque tells of the construction of the Berlin city lock in 1657 in outdated German. In honor of that occasion, a cornerstone plaque with an inscription was embedded within the structural components of the lock. During later modernizations in 1694 and 1863, the plaque was twice more brought out into the open. In each of those years another plaque was made and placed in the seawall together with the previous one(s). The last known find occurred in 1896 during the construction work on the Kaiser Wilhelm National Monument, which was directly adjacent to the lock. Again a plaque was made and walled in with the existing ones in a soldered zinc capsule.
This copper plate was donated to the Deutsches Technikmuseum by a private person who found it in her mother's estate. The circumstances that led to her coming into possession of the plaque are unknown. It is also not yet certain whether it is the original plaque from 1657 or a later copy. There is clear evidence that at least two copies of the two oldest plaques from 1657 and 1694 were made for the Märkisches Museum´s collection in 1869. The restorers at the Deutsches Technikmuseum are currently examining the object.
The exact location of the zinc capsule embedded in the base of the Kaiser Wilhelm National Monument is not known, nor is it known whether it is still there. Construction work is currently underway on the Freedom and Unity Monument (also known as the "unity seesaw"), which is being built on the base of the former Kaiser Wilhelm National Monument located in front of the reconstructed City Palace. It is thus possible that the zinc capsule could soon be recovered.