These fixtures were quite popular; the design in this photo was introduced in 1952 and continued in production through at least the early 1960s. All operated a 250 or 400-watt mercury vapor lamp that was powered by a separate ballast (or transformer) that was mounted separately. These were can-shaped and one is visible immediately above this street light's bracket. Nearly all mercury fixtures used in the industry that utilized a separate ballast also employed a remotely mounted photoelectric lighting control for dusk-to-dawn operation. Shown is a very rare example whereby this early fixture model employs the controller integral with the fixture. It was operated via glass tubes, like an old radio. By the late 1950s, fully solid-state photocontrols were introduced. These were much smaller and conveniently mounted on the newly designed "all-in-one" mercury fixtures which were built with their ballast and photoelectric control.