The 'Drillingsberichte' are a collection of 162 letters and a number of separately attached texts. The preserved original messages are made accessible through scans and transcriptions via the Bijzondere Collecties, of the Radboud University Nijmegen. The letters are generally typed by Felix and hand corrected by Gerda. A few letters were written by Gerda and occasionally there is a letter from 'omi' or 'mutti Gretl' in the collection. The 'Drillingsberichte' were written between 19 April 1937 and 25 October 1943.
Number of letters
Felix intends to write a letter every week, later he writes that he will write a letter every fortnight. In the first few years he keeps this up, but in the last few years the number of letters decreases. In summary:
|1940||23 + 4 other texts|
|1942||13, of one a 'testament'|
|1943||13 + one undated note|
The texts that are not letters include a typed speech for a birthday and fairy tales written by the children.
Whether the collection of letters is complete is not known. However, it seems likely, as the author Felix Oestreicher insists on keeping all the letters. Also, there seems to be no gap in the storyline between the letters. However, two letters have not been completely transmitted and stop at the end of the sheet of paper in the middle of a sentence. These are the letters with the dates: 24 August 1938 and 3 August 1942.
In a letter dated 16 July 1937 Felix writes that the letters appear in Dutch, German and Czech. This is a joke, because the language in the letters is German. The letters are written in German, with sometimes a word or a few sentences in Dutch. There are some exceptions, four letters are written in English and one in Dutch. The letter in Dutch is one of the last letters, dated 8 August 1943, in which Felix thinks that from now on the letters should be written in Dutch, but he actually doesn't do this. The English letters are dated 2 October 1939, 31 December 1939, 28 January 1940 and 14 April 1940.