German E.S. Code Disks
Frode Weierud  explains the purpose of this encryption system. "These disks were used to prepare coded recognition signals. In total there were five large and five small disks. The small disks carried the code names: Schmidt, Schilling, Schneider, Schulze and Seidel - all of these being German family surnames.  The large disks carried the code names: Eberhard, Ernst, Erasmus, Egbert and Emil - all German first (given) names. A small disk would be placed on top of a large disk, and the correct combination given as a complete name e.g. Egbert Schneider. Exactly how the disks were used to encode the recognition signal is not known at this time.  When the large and small disks are mated, they always render the initials "ES".

ES probably stands for Erkennungssignal (Recognition Signal). The reference number M.Dv. Nr. 111 probably refers to the disks themselves while the instructions for their use is probably given in the document "Auszug aus der "E.S.-Vorschrift" und Vorschrift "Der Erkennungsdienst" für U-Boote, Berlin 1940, M.Dv. Nr. 75a. (Extract from Recognition Signal Instructions and Instructions for the Recognition Service for U-boats, Berlin 1940)."

egbert_schneider_disk1.jpg
Image submitted by David Hamer, NCM Foundation
 
egbert_schneider_disk2.jpg
Image submitted by David Hamer, NCM Foundation

David Hamer also adds the following. "Information to date suggests that were five of each of the smaller or 'S' disks [10 Cm] and the larger 'E' disks [13 Cm] and that they were used in concentric pairs for some kind of coding purpose. In a videotape of the reunion of survivors from U-352,  one can clearly see a sample of the smaller disks labelled 'Seidel', which suggests that the large disks were given common German first names beginning with 'E' while the smaller disks were given surnames starting with 'S'. A collection of artifacts known to have been recovered from the radio room of U-352 contains, in addition to the 'Seidel' disk, two of the larger diameter disks, 'Ernst' and a further example of 'Egbert'.

A set of five such disk pairs were recovered from U-505 by the US Navy. They were labelled: Eberhard, Egbert, Emil, Erasmus and Ernst/Schilling, Schmidt, Schneider, Schulze and Seidel. Each of the larger disks has 58 sectors labelled 1-31 in an irregular fashion [days of the month..?]. Each smaller disk has 58 sectors, each labelled in random order 1-58.

The reference number M.Dv.Nr.111 means Marine Dienstvorschrift Number 111. The original form of this document, entitled "Funkbuch für Schießübungen" [radio book for shooting practice] was withdrawn from service in the mid-1930's and presumably the unassigned document number was then  re-assigned to the E-S disks"



Contributors and Credits:

1) David Hamer NCM Foundation.  <dhhamer(at)comcast.net>
2) Frode Weierud <Frode.Weierud(at)cern.ch>

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Jul 11/07