File photo from lightinggallery.net showing a maintenence person replacing (or removing) a Sylvania mercury lamp made some time during 1964-75. Mercury lamps produced in the 60s-70s lived with the highest performance (light output and longevity) far beyond their engineers and developers ever imagined! For instance, I know of several installations of dusk-to-dawn street lights that *still* have their 1960s mercury lamps still burning brightly! If not for the widespread HPS (high pressure sodium) conversions since the early 80s a great many of these original mercury lamps (and their built-to-last-forever) fixtures would still be lighting America!