A zelda rupee with a cavity. It can either be used to store something on some magnetic surface (e.g. the refrigerator) or two of them can be used together for a full rupee.
Depending on the printer you could require supports, but works on a Prusa MK3+ without supports.
It works well with semi-transparent green PETG. But when using semi-transparent filament increase the vertical perimeters and reduce the infill, to avoid seeing the infill pattern from the outside.
fits: 10mm ⌀, 2mm height magnets (e.g. https://www.amazon.de/-/en/Magenesis-Neodymium-Extremely-Powerful-Adhesive/dp/B06X977K8L )
The author hasn't provided the model origin yet.