It struck me that Amberel's elegant design bears a striking resemblance to a classic spiralling labyrinth. Such a structure certainly has relevance to the cache that this coin celebrates, for entry to the seventh circle is guarded by the great Minotaur, who normally resides in the labyrinth of Knossos.
Furthermore, scholars observe a distinction between a maze and a labyrinth. According to Wikipedia:
Maze refers to a complex branching (multicursal) puzzle with choices of path and direction; while a single-path (unicursal) labyrinth has only a single, non-branching path, which leads to the centre. A labyrinth in this sense has an unambiguous route to the centre and back and is not designed to be difficult to navigate.
I would argue that this also applies to il Nono Cerchio. There are not many alternative paths that may be taken (for more than a few metres anyway), so the navigation is generally "unicursal". That is not to say that the journey is easy, of course.
The ninth circle, however, is ultimately dominated by treacherous characters. This piece of silver now resides there; it should not be removed please, but it is hoped that it is discovered by any who venture to those depths.