dash vent differences

[Dakota]

I don't think I'm going to change what I have installed right now, but I am a bit curious on this question on which style dash vent goes with which year.   I have a 70 Challenger, standard (non-Rallye) dash with A/C.

The driver side dash vent has a knob for closing a damper on the back of the vent.   I have ended up with 2 different passenger side vents - one with a knob/damper and one without.      The center dash vent that I have, and all of them that I can recall seeing on the internet, lack this knob/damper arrangement.   Similarly, best I can recall, all of the driver side vents that I've seen on the internet for standard dashes have the knob/damper.  To make matters a little more confusing, the little louvers in the center dash vent and the passenger side vent that doesn't have the knob/damper are matched in appearance.

Which one(s) are original for the car and what do the other ones belong to?

Hard to believe I could almost buy a clutch for the prices that some of these vent pieces are being listed for.

[73chalngr]

My 70 se had passenger side damper. 

[EV2RTSE]

The driver-side vents I think were all the same from 70-74. The center & passenger vents with the wider chrome edge and the damper on the passenger vent were used in 1970. The center & passenger vents with the thinner chrome edge were 72-74 or 71-74. I think 1971 was sort of a transition year in that some of the leftover 1970-style vents may have found their way into some of the early cars. I seem to recall seeing some 1971 passenger vents with the thin chrome edge but still having the damper like the 1970 style also. But by 72 the damper rod was gone from the passenger vent.