| 摘要 |
The invention concerns a tile having a display surface exhibiting a plurality of teeth provided with two transversal surfaces. A visual symbol is reproduced on a first series of parallel surfaces, while on a second series of parallel surface, which are transversal to the surfaces of the first series, a further visual symbol is realised different to the first visual symbol. An observer views one or another of the visual symbols depending on his or her viewpoint.
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