The marking "EPVS A1" on a Kenson silver plate teapot indicates that the item is made of electroplated nickel silver (EPNS), which is a common material used for silver-plated items. The "A1" denotes a specific quality or thickness of the plating, often indicating a higher quality of silver plating. Kenson is a brand associated with silver-plated goods, and this marking helps identify the teapot's manufacturing details and material composition.