Fluorescent lamp, 1967.
Lamp, inspection, with circular fluorescent tube and magnifier, 1967, P.W. Allen, Ref.M.5
Inspection lamp with circular fluorescent tube and magnifier, 1967. An electrical discharge in mercury vapour and argon (or other rarified gas) produces the ultra violet light. Fluorescent materials on the inner wall of the glass tube convert the ultra violet into visible light.