Door vent flaps

Never seen these before, were they fitted to all cars? 

VW Golf mk1 door vent flaps 171819469A https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F163829721526

Not sure when VW started to fit them, I've got them on my 1988 cabriolet, they are held on with a plastic strip which over time falls off and so does the flap and can usually be found sitting on the bottom inside of the door.  

These have been fitted since the Golf Mk1 was produced in 1975, the Cab in 1979, Caddy in 1983 and all VWs, Passat, Jetta, Polo, Derby, Scirocco including Audi 80,90 & Avant in the 70s-90s era.

These are fitted to allow venting of the car via the doors and to prevent moisture coming from the internals of the doors during wet weather.

Hope this helps.