Probably been asked a million times, but the search doesn't bring up anything. :embarassed:
1) Can somebody tell me if this were a factory/dealer retrofit on a 90 16valver, or are they after market?
2) If a car doesn't have them fitted, I presume I won't need to remove anything to check to see if the handle has been 'punched' with a screwdriver?
3) Can these be easily retrofitted, and if so can I buy the bits from VW (I guess that will depend on the answer to Q1) or a specialist etc, and how much are they?
TIA
Kevin 
Back on topic...
1, Door plates were not a O/E part, but, dealers did fit them, usually as part of a package that was insisted on by insurance companies at the time, Door plates, alarm/immobiliser, steering wheel lock, were all par for the course, on any hot hatch, from the mid 80s on.. Golfs, Astra's and Escorts being particularly easy targets
2, Correct, though it would be worth checking to see if your car has been repaired around the door lock, and treating the back of the repair to a shot of some sort anti corrosion/waxoyl product, easy acsess with the door card removed..
3, Plates could easily be fitted.. VW probably dont stock them any more, GSF would have them though
Personally, I would recommend NOT to fit them... here's why, the doorskin can still be punched, in the same way, doing even more damage, especially if the plates are already covering up old damage! repair of the original configuration, is straightforward,
If someone wants to steal from you car, they're more likely to put a window in! If they want to steal your car, then they would need the keys, if you have an immobiliser fitted that is? and, more than anything , they look really crap!
Tom