1978, Gerald L. Howett, Kenneth L. Kelly, E. Thomas Pierce, Emergency Vehicle Warning Lights: State of the Art, U.S. Department of Commerce, National Bureau of Standards [NBS Special Publication 480-16], part III, chapter 10.6, 105:
The lamp is a PAR-36 “sealed beam” (internally reflectorized) unit of the type (designated #4416) most commonly used in rotating emergency vehicle warning lights. The lamp, operated at its design voltage of 12.8, draws 30 watts and has a peak intensity, as seen in the graph, of 35 kcd (= 35 kilocandelas = 35,000 candelas).
