There is a scale of 10 cun (1/3 decimeter) on the front of the bronze ruler.  In the grid of each cun engraves  mountains, houses and birds in the painting style of the Northern Wei DynastyIt wears severely after used for a long time. Hence it seems to be  a  ruler of daily use. 
The officials of the Northern Wei Dynasty used  “Da Dou” (volume measure with larger unit),  “Chang Chi” (ruler with longer unit) and “Zhong Cheng” (steelyard with larger scale) when collecting rents, in order to pay more taxes to the country  to obtain political achievements and increase their own income from grain, cloth and other in-kind salaries.  One chi (length unit) was 23-24 cm in the Han Dynasty, and 25 cm in the Eastern Jin Dynasty and  the Southern Dynasties. However, one chi  was nearly 31 cm in the Northern Wei Dynasty which was contemporary with the Southern Dynasty.