This is a large specialty fire nozzle by the Spaco Co in Burlington. Mass. These were used on fixed fire extinguishing systems that activated automatically. This is equipped with a aluminum cover that protected the nozzle from being contaminated by the process that was bring protected. When water was turned on the cover blew off allowing the nozzle to extinguish the fire.This nozzle is 5" long and is approx. 1 5/8"ID at the Female threads 130-331 is embossed on the rear of the nozzle. I don't know what that means.