How long after the initial run of sheet metal did the factory keep stamping parts?

The 70 Charger NOS quarter in the for sale section has a date way past 1970. work


56 Plaza 63 D100 step side 67 Coronet, 68 Roadrunner, 69 Super Bees, 69 Coronet 500 convertible, 70 Roadrunner Post, 79 D150 360, and a severe case of Mopar a,d,d