| 摘要 |
<p>A date disc has the numbers from 1 to 28 printed round its periphery and the numbers 29, 30 and 31 printed beneath the numbers 1, 2, 3 respectively. A week disc has letters, e.g. day abbreviations, covering four weeks which coincide individually with the numbers on the date disc. One of the discs has letters representing months and a device is provided to obscure any unwanted month indicatin. The week disc is pref. made of transparent material and the leters representing the months are pref. printed on this disc. The obscuring device may be in the form of coloured segments on parts of both discs. Alternatively these letters may be printed on the date disc with the coloured segments on the other.</p> |
