Refers to the imprint of the maker, customizer, or supervisor that is stamped with a seal or engraved with a knife on the bottom, inside the cover, or under the handle of the purple clay pottery.

Zisha style and ancient printed pottery are in the same line, and it is the continuation of ancient printed pottery. The purple sand seals we can see today have many similarities with ancient printed pottery, and they are also similar to ancient sealing clay. The purple sand inscriptions were first engraved and then developed to be sealed with seals.

Nowadays, it is generally not necessary to engrave the money directly. Compared with ancient printed pottery, purple sand inscriptions have unique characteristics: first, the engravings are mostly in regular script, which has the legacy of the Jin and Tang Dynasties. The style and style stamped with a seal. Many seals from the Han Dynasty and the Ming and Qing Dynasties are similar. Some seals directly borrowed seals from famous artists. For example, Gu Jingzhou used a seal with the words "It's enough for me to be interesting and old", which was a copy of the work of Wu Xizai, a seal engraver of the Qing Dynasty. The characters used in Zisha inscriptions are mostly regular script, Xiaozhuan and Miaozhuan. Appreciating the purple sand style from the perspective of calligraphy is far less rich and fresh than the ancient printed pottery. Most of the seals used in Zisha stamps are regular and strictly decorated, and have certain artistic and appreciation values. Some seals may be self-made by craftsmen, which are relatively crude and often have incorrect wording. Secondly, in addition to the content expressed by the Zisha stamp, in addition to the producer, customizer, supervisor, chronology, etc., there are also names of restaurants, halls, rooms, and many other meanings. Trademarks also appeared, but the content of ancient printed pottery was much monotonous. This is inseparable from the development of seals (zhai, guan, and shi seals were only used after the Tang Dynasty) and the development of the commodity economy. There are zodiac seals in ancient printed pottery, which have not been seen in purple clay models. Third, purple sand has gained a reputation, which is one of the signs that it has transformed from a practical product into a work of art. In this way, there are famous works that are easy to appreciate and identify. It is not surprising that the style and works are integrated into one, and a pot of gold is worth a thousand dollars. The number of enthusiasts, collectors, appreciators and researchers of purple clay pottery is increasing day by day, which promotes the development of purple clay art.