Diplomatarium Norvegicum Bind XXIII is the twenty-third volume in the Norwegian series of medieval source material publications since its inception in 1849. Work on volume XXIII was initiated already in 1995 and covers the period 1285-1562. The bulk of the diplomas transcribed in the volume are from the sixteenth century, which in Scandinavia was a period of political turmoil. The Kalmar Union, which since 1397 had united the three Scandinavian realms of Denmark, Norway and Sweden, was in dissolution with Sweden leaving the union, and the kingdom of Norway becoming integrated in the state of Denmark. The diplomas predating the sixteenth century concern issues such as Norway's relations with its North Atlantic dominions (skattland), as well as the Hanseatic League.

The publishing of medieval source material in the Nordic countries are nationally based projects initiated during the nineteenth century. During that century, five series were initiated: Diplomatarium Danicum (Denmark), Diplomatarium Suecanum (Sweden), Diplomatarium Norvegicum (Norway), Diplomatarium Fennicum (Finland) and Diplomatarium Islandicum (Iceland). The type of source material published in these series is exclusively diplomas. When researching the Scandinavian Middle Ages, diplomas are a problematic source material. Latin literacy, and its system of archives, written correspondence and legal documents, was introduced to the region mainly through Christianization and the ensuing institutionalization of the Church. Thus, Scandinavia became part of the Latin literary culture comparatively late; it is believed that in Sweden, Latin literacy became dominant only by the end of the thirteenth century. Moreover, until the late Middle Ages, comparatively few diplomas were promulgated. In the fifteenth century an increase in promulgated diplomas occurred, including a wider range of social groups as well. However, this increase in diplomas is of little help to the scholar; most of the diplomas promulgated have since been lost. In the case of Norway, it is estimated that approximately 20,000 diplomas have survived. Still, the situation is not entirely hopeless; new diplomas do appear, most recently through the increased accessibility of parts of the Apostolic Penitentiary archive, which has proven to contain hitherto unknown documents regarding the Nordic countries.

The series of the nineteenth century are regarded as an expression of the growing sense of nationalism and need for a national identity, which was prevalent at the time. This is particularly the case with Norway, which remained part of the Danish state until 1814, when it instead entered into a union with Sweden, which was to last until 1905. The diplomas included in Diplomatarium Norvegicum have been selected on the basis of either being promulgated in Norway or being deemed to concern Norwegian issues. However, based on these criteria the selection process became arbitrary, especially regarding the fourteenth-century source material when Norway and Sweden for several decades were united under the rule of King Magnus Eriksson. These problems are caused mainly by forcing a nation-state framework onto a time period when Scandinavia was an integrated political and economic arena. Moreover, it should be pointed out that Diplomatarium Norvegicum is not the only series struggling with these issues. For example, when initiated, Diplomatarium Suecanum used the nation state of nineteenth-century Sweden as a reference point and consequently includes documents from regions of Sweden, which until the Roskilde Peace Treaty of 1658 had been a part of the Norwegian and Danish realms, respectively.

The framework of the nation state not only affects which diplomas are included in a particular series, it also affects which time period is covered. Thus, Diplomatarium Suecanum covers the Middle Ages until 1540, Diplomatarium Norvegicum until 1570, while Diplomatarium Danicum ends already in 1412. A project is currently undergoing, which will extend Diplomatarium Danicum until the year 1450. These diplomas will be published through the already existing Diplomatarium Danicum online database. However, the additional diplomas will be published thematically and not chronologically.

Neither does Diplomatarium Norvegicum publish the diplomas in chronological order. This choice was made already by the editors of the first volume in 1849 and it has been upheld ever since. The positive aspect of this choice is that a large number of documents have been made available comparatively quickly and easily. The negative aspect is that the scholar is forced to work with several volumes simultaneously. This problem has been partially solved by the introduction of Diplomatarium Norvegicum as an online database. However, the online database has not been synchronized with the published editions. Therefore, at the time of publication of this review, neither the twenty-second nor the twenty-third volume of Diplomatarium Norvegicum have been made available online.

Despite the issues discussed in this review, Diplomatarium Norvegicum and its siblings are great resources for the scholar. As the volumes that have preceded it, Diplomatarium Norvegicum Bind XXIII is easy to use. The volume consists of three parts. The first part contains a foreword and an introduction, together with a list of abbreviations used. The first part also provides the reader with a detailed description of the principles behind identifying and naming the places of promulgation. The second part contains the diplomas. In total, 907 diplomas are printed here. Each diploma comes with an individual number as well as a summary in Norwegian. After the summary follows the diploma in its original language, a description of any seals found on the document, and additional notes. The included documents are the identified originals of copies available in various archival institutions. Great effort has been made by the editor to locate those originals. When this has not been possible, it is mentioned with the published diploma. The included documents are kept in a total of twenty-five different archives, located in all of the Nordic countries, except Finland, and in northern Germany. The third part of the volume contains thorough indexes of names of places and individuals mentioned in the documents.