This has been knocking around my desk since 1967. 27 mm, 11.2 gr. It appears to be tin with a copper plug. The file mark has been there as long as I've known it and the colour doesn't seem to fade. The scan does no favours, as this is far more readable in hand. At least, the reverse is. The obverse does resemble James, but you wouldn't pick him out of a line up based solely on this image. The edge such as it is appears rounded. Contemporary circulating forgery perhaps?