The article is devoted to a town book known as Niederstadtbuch. The main attention is paid to the draft version (the so-called Urschrift) of the manuscript of this source, which is stored in the Scientific Library of Tomsk State University. The source, mainly, contains information about loans. The Latin name of the book was "liber debitorum". One of the issues which the article focuses on is proofreading. First of all, the text bears corrections which were of a semantic nature. Of particular importance was the study of the strikethrough positions. Their number is 61 crossed out positions. In the course of the research was established the logic of the records' creation. The creditor personally applied for registration of the record in the office. Cases in which it was stated that the debtor's record was made in the absence of the creditor could most likely be considered an exception to the rule. Most likely, the creditor either initiated the cancellation of the record itself or through its authorized representative. The debtor may also have initiated cancellation, as evidenced by the reference to its being held liable for it. In addition, several hands of scribes were found, including one based on a clean version, the so-called Reinschrift from the Lubeck archive. The first secretary was Theodore. In most cases, he certified the entries in the book, but in some cases, his hand was also used to write the main text. The second secretary was Johann Lebrade. The third secretary was Hartwick Brekewalt. A comparison with the Tomsk manuscript revealed that his hand also appears in the draft of the source under study.