The dataset contains archival materials—typescripts of the principles on which Polish inheritance law of 1934 was to be based. These materials are held in the Archives of the Polish Academy of Sciences and the Polish Academy of Arts and Sciences in Kraków. The materials cannot be made fully available because I do not have the necessary permissions. These materials were used in the following articles: 1. Nancka, G., & Adamczyk, T. (2025). The challenges, difficulties and achievements of the Codification Commission of the Republic of Poland (1919–1939) in the field of succession law. Studia Prawnicze KUL, (4), 55–75. https://doi.org/10.31743/sp.18862, 2. Nancka, G., & Adamczyk, T. (2025). The Significance of Archival Sources in the Reconstruction of the Legacy of the Codification Commission of the Republic of Poland in the Area of Succession Law, [in:] Mikołajczyk M., Nancka G., Sadzikowska L., Rediscovering the Heritage of the Past, Göttingen 2025, p. 43-62.