The info on a vehicle comes from VW's Wolfsburg headquarters, specifically the archive in the VW AutoMuseum (not the AutoStadt just beside the factory). VW's archives there still have all the info on every specific VW that came off the German production lines - date of manufacture, model type, paint colour, accessories fitted, date of delivery, place of delivery, etc etc. The Autostadt can prepare a 'birth certificate' on a specific car, if you give them the chassis number and/or the engine number.
This is great for European and UK VW enthusiasts, as their VWs came from Wolfsburg (or other VW factories in Europe such as Emden, Hanover, Osnabruck, Ingolstadt etc). It's also great for US enthusiasts, as American-sale VWs also came from Germany. Americans never had a VW factory; at least not until the Golf (Rabbit) was built there from 1978. Mexican VWs were never sold in the USA either. So ex-USA cars are also German, and will be fine for the certificate.
To get a VW Birth Certificate for your German-made VW, just apply at the link below. It will cost 50 Euro. and takes about 6 weeks.
http://automuseum.volkswagen.de/urkunden.html?&L=1
But as mentioned, this won't work for the majority of our VWs, as they were made in Melbourne, not Germany. The AutoMuseum has no records on Australian production.