The new national core curriculum has been put into operation in Finland. Teaching and learning is intended to focus on historical literacy. In this paper, we study how it can be assessed with a pen-and-paper test, and what that reveals in regards to the mastering of historical literacy among elementary pupils. To study this, we designed a test where pupils analysed sources, answered open-ended questions, and filled out weighted multiple-choice questions. Furthermore, we implemented the test with the think-aloud method. The results from this indicate the way 12-year-olds read historical documents and formulate their own interpretations. The results demonstrate that most of the pupils succeeded in acquiring historical information from different sources, as well as understanding the interpretative nature of historical knowledge. The test also revealed that pupils can identify some intentions of the sources' producers, as well as reasoning through their own interpretations using a single source. Some pupils, however, could not process the cognitive noise inherent to the test (i.e. conflicting sources). Some of them also considered an authoritative source to be principally more reliable than other sources. Our study sheds light on which kind of task can be used at the elementary level to assess historical literacy.