Catalogue description Government Code and Cypher School: German Section: Reports of German Army and Air Force High Grade Machine Decrypts (CX/FJ, CX/JQ and CX/MSS Reports)

The summaries are loosely bound into books with hard covers. As the war progressed more material covering a shorter time-span was included in each book; also, because of time pressures, it was not possible to include all intercepted messages in the summary reports; many such messages where attached to the reports and bound in the same book. Again, at times of high activity reports were compiled some days after the dates of the messages covered. Sometimes too, the serial numbers seem to have been taken out of sequence but to maintain continuity the reports were filed in serial order. As books therefore cover overlapping time frames, the dates given in the list should not be taken as completely definitive.

Several series of reference numbers were used for the issue of reports until the CX/MSS/... series was begun in June 1941; a new series was introduced in mid-November 1943: e.g. R1(A), R1(B)... etc., R2(A), R2(B)... etc. Separate series were used to indicate British intelligence analyses and assessments of the Sigint reports. At the beginning of most books are lists of radio frequencies and times of interception relevant to items in reports in the books. Many reports also have an attached signals/communications supplement in SDE series.