When a rectangular shape is selected in the modification or creation of a new coin/exnumia can the diameter field be disabled and a new field of length/width be shown instead or follow the banknote method of a size field. The diameter is an inapproriate field for a rectanugular shaped coin/exonumia.
I believe the guidelines should also be updated to reflect this.
I think putting the height and length in the additional information field of the shape and the diameter as size has its merits. I only use coin flips with round windows, right now I can see right away what kind of flip I need.