This note presents a detailed analysis of a recently acquired Charles I shilling. It’s weight was suspiciously low and the colour not quite right. XRF analysis reveals a low silver content and the density confirms the alloy to be almost pure copper. Apart from the curious alloy it is an exceptional cast copy of a coin that is a die duplicate of Brooker 434. Unless any compelling evidence of more recent manufacture is found, e.g., the discovery of more identical specimens or further analysis reveals unexpected metals, I am inclined to consider this to be of near-contemporary manufacture.
Also see:
BNS Research Blog 