early 20th century (c. 1915-1925) completely intact and fully functional antique american industrial or medical "doctor heat" light therapy lamp possibly designed and fabricated by or for the spear-marshal company, republic building offices, chicago, ill. the unusually designed desk light features a deep bowl rolled rim solid copper metal reflector or shade with a brilliant finish. the cast iron base with distinctive "sunburst" or embossed radiating sun ray pattern really adds visual character and reflects the purpose of the lamp as a source of illumination for therapeutic purposes. by the 1920's and perhaps beyond "light therapy" reached its peak as a method for healing numerous ailments or illnesses revolving around skin disorders mental instability and so on. phototherapy combined some scientific knowledge with a plethora of popular speculation as to its healing properties. the lamps manufactured came in all shapes and sizes with a combination of filters for harnessing certain types of light along the electromagnetic spectrum. the tilting or pivoting arm adjusts the angle of light. the socket housing is comprised of steel. a standard incandescent light bulb can be used to repurpose the fixture into a regular desk or table lamp. the brushed metal finish has been sealed with a clear coat lacquer.