The book was never captured, but the indicators were broken and a skeleton code book constructed by Ross of Naval Section in 1941. The reconstruction of the book was simplified by the acknowledgement from Control of every Rossary that was sent, the acknowledgement giving the sense of the Rossary.
b) Short E-Bars (U-Bootskurzsignale).
The U-Bootskurzsignalheft (1940) was a 10 page phrase book specially designed for U-Boats. Phrases had 3 letter equivalents, a+c = g (mod 26). Example:
TTT Will be at Port of Arrival in 36 hours.
TUV " " " " " " " 30 "
Message settings were obtained from indicator tables of which 3 varieties are known:
BREMEN - in use until 12.5.41. Two tables of 26 settings for odd and even months as for Rossaries. The indicator letter appeared in the preamble of the signal.
DRESDEN in use 12.5.41 -- 5.10.41.
AUGSBURG in use 5.10.41 -- 1.1.42.
Dresden and Augsburg each consisted of two tables (for odd and even months) of 132 settings, there being an unique setting depending on day of month and time of origin. No indicator was transmitted.
When Dresden and Augsburg were in force a cypher signal consisted of
Time of Origin.
One cyphered group (rarely two).
The phrase book -- with Bremen and Dresden -- was captured in 1941. Augsburg was partially reconstructed from cribs obtained from Control's acknowledgements.
c). B-Bars (Standortmeldung als U Bootskurzsignal) up to January 1942.
The Short E' phrase book contained no code groups equivalent to Naval Grid Squares, but gave instructions as to how these should be sent in a short message using the same indicator tables. The prefix B'B' replaced E'E' and the first 3 letters of the decode gave not a 3 letter book group but the grid position to 2 figures - omitting the first letter and with figures off the top row of the key board.
e.g. AL34 would be given as LER