The advantages of aligning custom data schemas with standardised ontologies within their respective knowledge domain have long since been proven in practice. Sharing a common structural representation by mapping concepts and relationships between the schemas is essential to ensure data interoperability (especially on a semantic level), integration, reuse, and the ability to leverage machine-processable and advanced-search capabilities. Archival institutions preserve, manage, and provide access to large amounts of diverse cultural and historical data, demonstrating a high potential to be active contributors to a global knowledge network, should archival data be transformed and offered as linked (open) data. The present study aims to improve the alignment of the Swedish National Archives schema to a core ontology for archival resources description (Records-in-Context Ontology - RiC-O) by producing conceptual mappings between them and reusing as many elements and relations as possible from Records-in-Context. The produced mappings were evaluated ex ante by domain experts and integrated in the Swedish National Archives schema as new RDF representations. Apart from the purpose of enabling the process of transforming archival data into linked data, the conducted research aimed to contribute expert-curated data for future experimentation on introducing automation (e.g., use of LLMs) in the semantic alignment and mapping process.