My advice is just have a good look round it and if it don't feel right, walk. I've bought probably fifteen used anniversaries (not for myself you understand) but seen fifty. They range from the immaculate concours examples to the boy racer sheds. Obvious points that I can think of are:
Wheels as already mentioned. These are a bloody nightmare and horrendously expensive. They are that gunmetal colour which means they cannot be refurbed by the normal mobile chaps. Peopl still try it though!

Numbered plaque. There will be a numbered plaque on the side of the dash on the offside only visible when drivers door is open. If this is here and shiney, it's a good indication that the previous owner is proud of it.
Badging. Make sure all original badges are in place. If not why not?. Is there any sign of paint damage where they were removed?
Front spoiler. Sits a bit lower than normal so prone to scratches.
It's worth remembering as well that a lot more than you think is unique on teh GTI Anni. The headlamps(darkened and more expensive), steering wheel, gear knob, headlining, seats (obviously). A cracked headlamp is worth getting a quote for first as they are unique to the GTI Anni.
0202 with 50k at 11990 sounds pretty good car is good. I've just bought another for more than that but with less than half the miles which i'll put up for 13495 ish. The low mileage ones are more desirable but the one you've seen is probably one of the cheapest main dealer cars I've seen.
VWmd