Spout Side Line with Antique Yixing Clay Teapots

I have collected hundred of Yixing Clay Teapots over the years, mostly of old and antique teapots. What's puzzling me is that some of these teapots have lines on the side of the spout, even with top quality masterpieces

Kebo ChengJia teapot of late Ming 明刻薄成家壶

XIANG Zijing Molin teapot of late Ming 明项子京墨林壶

CHEN Mingyuan teapot of Kangxi reign 清康熙陈鸣远冷眼壶

Qingquan Meiyu teapot of Tianqing clay of mid Qing 清清泉美玉天青泥松根壶

Qing YiXing Zisha Clay Teapot QianLong (Chien-lung) Imperial 大清乾隆年制壶

I do not know how these teapots were made. One possibility is that they indeed were made with the help of Tools or even moulds. Even if that's true (which we don't know for sure), they can be just as valuable if they were not massively produced. I believe that should be true considering the much smaller market hundreds of years ago.


Considering the top teapots we have with the examples above, basically we should ignore the line at all for antique teapots.