It seems Bianchi began in 74 as a project between John Bianchi (a holster etc maker) and Don Keller formerly of Kel Lite and Kel-lite in 68/69-ish, Streamlight around the time Kel-Lite got going good, but were focused on mega output spotlights at first, mag in 78 or 79, SureFire in the late 80's.
But a fellow named Conrad Hubert passed out a bunch in the 1920-ish era and they were a big hit for Eveready. They did some 2C Soldier Boy models for soldiers in WW1 that were later used by police. Franco made some duty lights, and so did French Flasher/Rayolite, now Rayovac. CF Burgess did some and so did BriteStar way back then. By the late 50's Dog Supply House was doing search and rescue lights along with Rayovacs line of Sportsman. Fulton famous for the right angle light also did cop lights.
Some antique duty lights.
A Dog Supply House 6D with Hi-Bred extension.
This Olin had a built in traffic wand.
A really early Franco cop light circa 1915-ish.
Patent-kleptos Pentagon did some good stuff.
Pelican should be mentioned as well. But I do not know the beginings of either of those.
But the Bianchi and Kel-Lites changed the game to what we now consider duty lights.