A handwritten “1” was found on a North Korean artillery shell collected from Yeonpyeong Island following the North’s artillery attack on the island Tuesday.

The distinct marking was found where the propellant charge of a 122-millimeter artillery shell was located.

The North manufactures weapons through an automated process. But the last phase of the assembly is carried out by hand, including the marking of numbers.

A military official said that the discovery is similar to a finding made during the study of a North Korean torpedo that was found at the site where the South Korean naval ship, the “Cheonan,” went down in late March. At the time, a handwritten “1” was found in the area where the torpedo’s propellant was located.

The official said the latest finding will help eliminate suspicions that the “1” on the torpedo was fabricated.