70 Duster Drip Rail Trim Question

Well, I know it wasn't standard. I also have a '70 Duster that is all original and no drip rail trim, also a '74 Duster without it. I also had a '72 Duster a while ago without it. These are/were all plain roof cars.
I've seen the drip rail trim mostly on vinyl roof cars....both canopy and full styles.
It may have been optional on plain roof cars....maybe someone else can confirm that.