That could be an TwinSonic 12E, but the mounting is not Federal Signal. The mounting feet on the bar look similar to those of a later production Signal Stat cross bar.
It does look like a Signal Stat bar. If it is, those are suction cups, not magnets and had brackets to hook on the rain gutters. I used to have one of those bars (with SVP pancake lights) on an '83 Nissan P/U...
Look closely.. you can see the mounting bar has the mounting circles for 2 beacons, they just took the beacons off of the bar, and bolted the twinsonic to it. Most likely was a wrecker that "upgraded".