In US that Certificate of Origin (COO) along with the gold CMC tag is the official title for the fiberglass kit body of the Speedster. If it's on a VW pan, that and the VW donor car will get the replica registered in most states. Often builders just use the VW title that matches the donor's pan VIN.
I have the same COO and gold id plate for my 1988 CMC. I don't know where those COOs are registered (or if they are) but they are an official "title" issued thru State of Florida - they is no certificate of authenticity other than that watermarked document. I don't know if FL records or tracks the COO (CMC went belly up in 1992). State titles use a similar paper.