_En revanche_, the K'ang Hsi mark is freely used on quite modern wares, that period being now regarded as classical; so that we are confronted with the paradox that if a specimen of fine quality[450] is marked Ch'êng Hua, it may generally be assumed that it was made in the K'ang Hsi period, while the bulk of the pieces which bear the K'ang Hsi mark are of modern date. The Yung Chêng and Ch'ien Lung porcelains are highly esteemed to-day, and consequently the marks of these periods are considered worthy of a place on modern imitations; but on the whole the bulk of the specimens bearing these marks will be found to belong to the period indicated, and the imitations are generally so coarse as to be unmistakable. The temptation to borrow the reign marks of the subsequent periods is so slight that we may safely accept the later marks as correct indications of date. Marks written in enamel colours and even in gold become increasingly common on the _famille rose_ porcelains from the Yung Chêng period onwards, the red mark being more familiar on the modern wares than the blue; and seal characters frequently replace the ordinary script in the reign marks of the Yung Chêng and subsequent periods. Date marks in seal form before the eighteenth century are very unusual, and should be regarded with suspicion. It will be seen from the foregoing notes that Chinese date marks must be treated with great caution. In fact it is safer to regard them merely as secondary evidence, first basing one's judgment on the paste and glaze, the style of decoration and the quality of the colours. The one exception to this declaration of unfaith is the marks on the Imperial porcelain. These would naturally be correct and reliable, except where deliberate imitations of the older wares were undertaken; and then, no doubt, the mark of the period imitated would be used to make the illusion complete. The Imperial marks were the work of calligraphers who were selected for the purpose, and the writing is careful and in good style. In fact a well-written mark is almost as certain a sign of Imperial ware as the five-clawed dragon itself.[451] At the private factories the marks were often carelessly, even illegibly, written, and probably little trouble was taken with this part of the decoration except on the choicer specimens. On a large proportion of the private wares the mark was omitted altogether. The marks on Chinese pottery and porcelain may be conveniently grouped under the following headings:-- (1) Date marks. (2) Hall marks. (3) Potters' names and factory marks. (4) Marks of dedication, felicitation, commendation, etc. (1) _Date marks._ The date marks conform to the two Chinese systems of chronology, (_a_) the cyclical and (_b_) the reign names of the Emperors.