English, c.1945, marked Thackary, chrome plated tester with 6 prongs,

Note: A tuberculin skin test is employed to determine if an individual has been previously exposed to the bacteria responsible for tuberculosis. Six sterilized needles are immersed in tuberculin and then utilized to puncture the skin. The emergence of a red, firm area signifies past or present exposure to the bacteria, suggesting the person may have the disease, possess natural immunity, or have acquired immunity through some means.