| 摘要 |
The disc has a top wall and at least one central region formed by a calotte-like central wall. Within the top wall (3) there are several runner grooves (10) for balls (11). The grooves are spiral-shaped and form a labyrinth. A transparent cover is provided on top of the top wall. Side plates (5) are provided on two sides of the top wall, and theses have holes (13) for receiving an anchoring element (14) attached to a string (15).
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