The fonds consists of 26 letters, dated between March and October 1915 and five postal receipts. It has been arranged in chronological order, the letters in folders numbered 1-26 and the receipts in a separate folder. Four of the letters were sent by Ada Hartmann to her husband, the remainder being sent by Otto to her. His letters reflect various experiences in the war, with many references to his company's movements and activities, to the transportation and work duties of the prisoners, and to the ranks, salaries, uniforms and weapons of the Prussian Army. He also touched on non-military topics, including singing, cigars, and other social matters. Among the people named in his letters were: battalion commander Major [Flienitz?]; Oberstleutnant Kuntzel; Vizefeldwebel Vick; Victor Ansaux, a prisoner at Münster; and the family of Paul Voss. Most often comprising only one folded page, his letters were sent by Feldpost, the postal service of the German Army. The letters from Ada, which were typically longer, often concerned various household purchases, payments into the Militärdienst-Versicherung (military service insurance – see receipts below), and such events as a trip with the children to Hagenbeck Zoo. Both wrote in the Spitzschrift or Kurrentschrift form of handwriting typical of the day, though Ada's writing was more flourished and regular than Otto's. Due to water damage and poor paper quality, the letters and envelopes are extremely brittle and are in places very difficult or impossible to decipher.
Note: Although encapsulated, the letters are still extremely fragile and easily damaged. Researchers are asked to use the photocopies provided wherever possible to avoid further damage.
The five Posteinlieferungsscheinen [postal receipts], are postmarked in Minden and presumably obtained by Ada Hartmann. Each consists of a printed form filled out in ink. Three blue-green receipts were issued for small deposits made in 1916 and 1917 to an account with the Deutsche Militärdienst-Versicherung of the Hanover branch of Berlinische Lebens-Versicherungs-Gesellschaft (Berlin Life Insurance Company). The remaining two receipts were issued for larger amounts sent by postal order in the same period to Gotthard Luch in Homberg an der Ohm, Oberhessen (Upper Hesse).