Signedstamped on bulb: COOLIDGE / (GE logo) / TUBE / 5561
Inscribedstamped in white on tube: PAT. NOV. 8, '04 FEB. 27, '12 / DEC. 30, '13 MAY 16, '15 OCT. 31, '16 JAN. 12, '17 / PATENTS PENDING / THIS TUBE IS NOT LICENSED TO / RE(illegible)STED O(illegible) / NOR IS THE HEL(illegible) / TAINED LICENSE (illegible) / EXCEPT IN (illegible) / TUBE / GENERAL ELECTRIC / SCHENECTADY, N.Y.
FunctionStandard early Coolidge tube. The heated cathode emits electrons that are accelerated by a high voltage and strike a metallic target in the middle of the bulb to produce the x-rays. This unit has a very large bulb to dissipate the heat and has a relatively fine focus.
ProvenanceFrom the Harvard Medical School.