Hirtz's compass for locating projectiles in the body, brass and steel compass, brass limbs, steel pointers, Gaiffe, maker, Paris, France, 1915
The Hirtz compass was invented in 1907 by E J Hirtz, a French medical officer and head of physiotherapy at a military hospital.
The brass device was used to accurately determine where bullets were located in the body, especially the brain. Bullets could then be removed surgically with precision thereby reducing damage to the surrounding areas of the body. X-rays were also used to guide the surgeon. This example dates from the First World War.