That is genuine baked-on World War II army paint. It’s much different than the paint on my modern army things. The red primer and gray paint was applied over it, and it is not a baked on factory finish. It was probably shot out behind the motor pool.
In the war, they weren’t concerned about a show finish, so there’s no leveling primer or sandable primer under the green.
I believe they just hit the metal with a phosphoric acid wash as a primer, because there’s no color under this green except the faint black of phosphated metal.
That WW2 paint probably has chromate in it to make it stick good.
I programmed machines (primitive industrial robots) out at Vendo where they made vending machines. During the war, they made airplane parts and they sprayed this paint out there which is very toxic. They also did various electro plating operations.
All that stuff got into the ground water, and they did expensive steam injection for about five years. Eventually, they brought it all up out of the ground, so they could dispose of the highly toxic zinc chromate and hexavalent chromium etc.
That property became valuable as the town grew up around it, so they sold it and moved to a different county.