The Open Metadata Pathfinder project will deliver a robustly validated demonstrator of the effectiveness of opening up archival catalogues to widened automated linking and discovery through embedding RDFa metadata in Archives in the M25 area (AIM25) collection level catalogue descriptions. It will also implement as part of the AIM25 system the automated publishing of the system's high quality authority metadata as open datasets. The project will include an assessment of the effectiveness of automated semantic data extraction through natural language processing tools (using GATE) and measure the effectiveness of the approach through statistical analysis and review by key stakeholders (users and archivists). All outputs of the project will be integrated into AIM25 resources and workflows, ensuring the sustainability of the benefits to the community.