The setup includes:
(1) Model 616 Halogen Lamp
(1) Steel seat bracket
(1) Standard mounting bail bracket
(1) Nut and bolt
Available in Red  and Amber. 
All components are new old stock
This kit will work with a variety of vehicles. This mounts directly to the existing seat bolts on your vehicle. 
This and similar setups were widely used by California agencies in the 80s and 90s.
Includes a standard single flasher, FREE of CHARGE 🙂 This flasher will flash the rear light on and off. Flasher brand may vary from photo.