I just happened to have ESC opened near the right page when I read this post, your half groat is the first milled issue of Maundy Money referred as a undated Type C ESC2167A. The other undated types, D, F and B (don't ask what happened to A and E) have a & instead of ET. Don't take the term Maundy Money to literally for this period it is just a general term for small silver change.