We still have some here at the plant I work at as a clean agent extinguishing system for one of the control/MCC rooms. To Frank's point, if the discharge alarm rings it is time to exit because it totally floods the space with Halon. The only Halon left is reclaimed($$$) and while my supplier can get it we are slowly moving to other agents like FM200. I don't think you can legally put anything but Halon in a Halon bottle - CO2 bottles are heavier due to the much higher pressure.
We got to shoot Purple K from a large wheeled unit on a flammable liquid fire at school - good stuff and very effective. For vehicles, I've been installing a minimum of 5lb ABC drychems although some of the loaders and tractors carry 10lbs due to the large volumes of hydraulic oil and the hot times that can result
