ANSI C78.1431-1997 (R2016)

American National Standard for Electric Lamps – Slide Projector Lamps, Condensing, Dichroic, Two-inch (51 mm), Integral Reflector, Rim ReferenceTungsten-Halogen Lamps with GY 5.3 Bases
standard by American National Standards Institute, 06/01/1997

ANSI C78.1421-2002

American National Standard for Dimensions and Centering Systems for Projection Lamps – 35 mm Integral Reflector, Rim Reference Lamps with GZ4 Bases
standard by American National Standards Institute,