The stycas minted at York between about the 820's and the Viking occupation in 867 were made from an unusual alloy containing a high proportion of zinc. Drillings into the edges of 44 specimens allowed the authors to determine by neutron activation analysis the percentage contents of eight chemical elements. The cementation process and the implications of the useof tin in the alloy are discussed. A possibly contemporary lead-tin striking is published in an appendix. -- AATA