Back then, there had been a big tractor tire hung from a rack to mark the circle (back in Eagle Plains, I had seen the photos of the tire).
当时，出现了大拖拉机轮胎悬挂在机架上，标志圆(在鹰平原，我看到了照片的轮胎)。
2
In a method of manufacturing a pneumatic tire, after the raw tire is vulcanized, an identification mark is spray-painted on the tread face of the vulcanized tire.