Large archaeological, organic materials can be difficult to preserve, conserve, and store in their entirety, which is why prioritisation is often necessary. Priority is generally given to recognisable objects rather than smaller fragments. Nevertheless, for archaeological leather, exactly such insignificant fragments can provide new information on the diversity of species exploited. In this pilot study, we use a Citizen Science approach for the first time to identify archaeological leather fragments using the protein-based method Zooarchaeology by Mass Spectrometry (ZooMS). By inviting the public to participate in archaeological research, the project's first 52 samples, including both recognisable and unidentifiable objects, were analysed. We show that the participants not only generated good data, but also contributed to current knowledge by identifying two hitherto undescribed animal species for leather in medieval and Renaissance Copenhagen. The finding of deer suggests that Copenhagen citizens now and then had access to game through the nobility and the finding of horse suggests that the unclean status of horses was sometimes overlooked to exploit its hide. Our findings are promising for more identifications and the new knowledge the project will generate. The study calls into question how we prioritise and assign value to cultural heritage materials.