Those were a S&S exclusive light, available on their raised roof ambulances, with either a 7 1/2" flashing light or Federal Sola-ray light, and a small red bullet-shaped lens in the back. Either mounted as a shown, or with a third one in the center. My '67 came equipped with the two outer mounted lights, with Sola-rays, and the rear red lenses are on steady when the lights are powered up. It had a Federal Q2B mounted in between. As there weren't many (comparatively) S&S high tops built, they're not too common, but they occasionally come up for sale on eBay and such.